Aqueous dispersion of fluorocopolymer and composition for water-based coating material

ABSTRACT

An aqueous dispersion of a fluorocopolymer, which is excellent in stability and film-forming properties as an aqueous dispersion and which gives a coating film excellent in weather resistance and mechanical strength and improved in water resistance and stain resistance. The aqueous dispersion comprises water and dispersed therein a fluorocopolymer which comprises (a) polymer units based on a fluoroolefin, (b) polymer units based on propylene, (c) polymer units based on ethylene and/or (d) polymer units based on butylene and which has a melting point within a range of from 40 to 150° C.

TECHNICAL FIELD

The present invention relates to an aqueous dispersion of afluorocopolymer and a composition for water-based coating material.

BACKGROUND ART

Heretofore, a vinylidene fluoride type resin is widely used as abaking-type coating material, since it is excellent in weatherresistance, heat resistance and chemical resistance and it is soluble ina solvent at a high temperature. As such a vinylidene fluoride typeresin, a homopolymer of vinylidene fluoride or a copolymer of vinylidenefluoride with a fluoroolefin (such as tetrafluoroethylene,hexafluoropropylene or chlorotrifluoroethylene), has been proposed.Further, it is known that a copolymer of a fluoroolefin with cyclohexylvinyl ether and other various monomers, is soluble in an organic solventeven at room temperature, and when used as a coating material, it givesa coating film which is transparent and has high gloss and which furtherhas excellent characteristics such as high weather resistance, water andoil repellency, stain resistance and non-tackiness (JP-A-55-44083), andits use is increasing in the field of weather resistant coatingmaterials for interior and exterior of e.g. buildings.

On the other hand, in recent years, restriction on use of problematicorganic solvents has been increased from the viewpoint of theenvironmental protection against e.g. air pollution or the safety tohuman bodies, and social demand for an aqueous coating material or apowder coating material employing no organic solvent, has increased.Also with respect to a fluororesin, an aqueous dispersion type has beenstudied, and with respect to a vinylidene fluoride type resin, a methodfor emulsion polymerization of an acrylic monomer in the presence ofvinylidene fluoride resin particles, has been proposed (JP-A-3-8884,JP-A-4-325509).

Further, also with respect to a copolymer of a fluoroolefin with acyclohexyl vinyl ether and other various monomers, an aqueous dispersiontype has been studied, and it has been reported that such can beprepared by emulsion polymerization (JP-A-57-34107, JP-A-61-231044).Further, an aqueous dispersion has been proposed in which afluorine-containing copolymer having, as an essential constitutingcomponent, polymer units based on a macro monomer having a hydrophilicmoiety, is dispersed in water. This aqueous dispersion is excellent inthe film-forming properties and presents a coating film having goodmechanical strength, and it is reported further that it can be producedeven without using an emulsifier or a hydrophilic organic solvent.

However, with an aqueous dispersion of a vinylidene fluoride type resin,the stability of the aqueous dispersion is not necessarily good, and thetransparency of the coating film is poor due to the crystallizability ofthe resin, and if the crystallizability is lowered in an attempt toimprove the transparency, there has been a problem that the glasstransition temperature of the coating film tends to be so low that thestain resistance tends to deteriorate. By seed polymerization of anacrylic monomer, there has been some improvement over the problems, butsuch has not been adequate. Further, there has been a problem also withrespect to the film-forming properties. Furthermore, the vinylidenefluoride type resin is composed solely of a fluoroolefin, and the costtends to be high. A copolymer of a fluoroolefin with cyclohexyl vinylether and other various monomers is practically useful as thetransparency of the coating film and the film-forming properties aregood, but since a liquid monomer is employed, the coating film tends tobe slightly tacky, and a further improvement in this respect, has beendesired.

The present inventors have found that these problems can be solved by anaqueous dispersion obtained by seed polymerization. of an acrylicmonomer in the presence of particles of a copolymer of a fluoroolefinwith an α-olefin such as ethylene or propylene. Such an aqueousdispersion has a practical level of adhesion to various substrates, butthe adhesion to a glass or cement substrate has not yet been fullysatisfactory. Further, contaminants are likely to deposit thereon, andwhen it is used at a place where no rain will fall thereon, the surfacedeterioration of the coating film will be little due to high weatherresistance, and as compared with a coating film which is susceptible tosurface deterioration, a stain once deposited, tends to be scarcelyremoved by a slight force of rain water. Accordingly, there has been aproblem that as compared with a coating film which is susceptible tosurface deterioration due to inadequate weather resistance, it issusceptible to staining on appearance. Further, under severe weatherconditions, as a non-crosslinked type coating material, blistering orpeeling of the coating film is likely to result due to rain or sunshineoutdoors, and further, there has been a problem that the solventresistance is inadequate.

DISCLOSURE OF THE INVENTION

The present invention is to solve the above described problems of theprior art and has an object to present an aqueous dispersion of afluorocopolymer and a composition for water-based coating material,whereby the aqueous dispersion is excellent in stability andfilm-forming properties, and the fluorocopolymer coating film isexcellent in mechanical strength and improved in weather resistance,water resistance, solvent resistance, adhesion and stain resistance.

The present invention has been made to solve the above describedproblems, and according to the present invention, the followinginventions are presented.

(1)

An aqueous dispersion characterized in that a fluorocopolymer which is acopolymer comprising (a) polymer units based on a fluoroolefin, (b)polymer units based on propylene, and (c) polymer units based onethylene and/or (d) polymer units based on butylene and which has amelting point within a range of from 40 to 150° C., is dispersed inwater.

(2)

An aqueous dispersion characterized in that a fluorocopolymer which isthe fluorocopolymer as defined in (1) and which has a glass transitiontemperature within a range of from −20° C. to +80° C., is dispersed inwater.

(3)

An aqueous dispersion characterized in that a fluorocopolymer which isthe fluorocopolymer as defined in (1) and which has a value Q as anindex of its molecular weight within a range of from 0.1 to 10,000, isdispersed in water, provided that the value Q is a value defined by avolume extruded in a unit time (mm³/sec), when, using a flow tester, thefluorocopolymer is filled in a cylinder having an inner diameter of 11.3mm and then extruded from a nozzle having an inner diameter of 2.1 mmand a length of 8 mm under a load of 7 kg at 140° C.

(4)

An aqueous dispersion characterized in that a fluorocopolymer which isthe fluorocopolymer as defined in (1) and which has a content offluorine atoms within a range of from 20 to 65 wt %, is dispersed inwater.

(5)

An aqueous dispersion characterized in that a fluorocopolymer which isthe fluorocopolymer as defined in (1) and which has a particle sizewithin a range of from 50 nm to 300 nm, is dispersed in water.

(6)

An aqueous dispersion obtained by emulsion polymerization, in thepresence of 100 parts by weight of particles of the fluorocopolymer asdefined in any one of (1) to (5), of from 100 to 10,000 parts by weightof a mixture of the same combination of monomers as for said particles.

(7)

An aqueous dispersion characterized in that composite particles obtainedby emulsion polymerization of from 5 to 200 parts by weight of a radicalpolymerizable monomer mixture comprising, as the main component, analkyl (meth)acrylate having a C₁₋₁₈ alkyl group, in the presence of 100parts by weight of particles of the fluorocopolymer as defined in anyone of (1) to (6), are dispersed in water.

(8)

A composition for water-based coating material, comprising the aqueousdispersion of the fluorocopolymer as defined in any one of (1) to (6)and from 0.1 to 100 parts by weight, per 100 parts by weight of thesolid content of the fluorocopolymer, of the solid content of aninorganic/organic silicon compound, incorporated to the aqueousdispersion.

(9)

A composition for water-based coating material, comprising the aqueousdispersion as defined in (7) and from 0.1 to 100 parts by weight, per100 parts by weight of the solid content of the composite particles, ofthe solid content of an inorganic/organic silicon compound, incorporatedto the aqueous dispersion.

(10)

A composition for water-based coating material, comprising the aqueousdispersion as defined in (7) and a hydrazine derivative having at leasttwo hydrazine residues, incorporated to the aqueous dispersion.

(11) An aqueous dispersion characterized in that a fluorocopolymer whichis a copolymer comprising (a) polymer units based on a fluoroolefin, (b)polymer units based on propylene, (c) polymer units based on ethyleneand/or (d) polymer units based on butylene, and (e) polymer units basedon at least one member selected from a vinyl ester, a vinyl ether, anisopropenyl ether and an allyl ether and which has a melting pointwithin a range of from 40 to 150° C., is dispersed in water.

(12)

An aqueous dispersion characterized in that a fluorocopolymer which isthe fluorocopolymer as defined in (11) and which has a glass transitiontemperature within a range of from −20° C. to +80° C., is dispersed inwater.

(13)

An aqueous dispersion characterized in that a fluorocopolymer which isthe fluorocopolymer as defined in (11) and which has a value Q as anindex of its molecular weight within a range of from 0.1 to 10,000, isdispersed in water, provided that the value Q is a value defined by avolume extruded in a unit time (mm³/sec), when, using a flow tester, thefluorocopolymer is filled in a cylinder having an inner diameter of 11.3mm and then extruded from a nozzle having an inner diameter of 2.1 mmand a length of 8 mm under a load of 7 kg at 140° C.

(14)

An aqueous dispersion characterized in that a fluorocopolymer which isthe fluorocopolymer as defined in (11) and which has a particle sizewithin a range of from 50 nm to 300 nm, is dispersed in water.

(15)

An aqueous dispersion characterized in that a fluorocopolymer which isthe fluorocopolymer as defined in (11) and which has a content offluorine atoms within a range of from 20 to 65 wt %, is dispersed inwater.

(16)

An aqueous dispersion obtained by emulsion polymerization, in thepresence of 100 parts by weight of particles of the fluorocopolymer asdefined in any one of (11) to (15), of from 100 to 10,000 parts byweight of a mixture of the same combination of monomers as for saidparticles.

(17)

An aqueous dispersion characterized in that composite particles obtainedby emulsion polymerization of from 5 to 200 parts by weight of a radicalpolymerizable monomer mixture comprising, as the main component, analkyl (meth)acrylate having a C₁₋₁₈ alkyl group, in the presence of 100parts by weight of particles of the fluorocopolymer as defined in anyone of (11) to (16), are dispersed in water.

(18)

A composition for water-based coating material, comprising the aqueousdispersion of the fluorocopolymer as defined in any one of (11) to (16)and from 0.1 to 100 parts by weight, per 100 parts by weight of thesolid content of the fluorocopolymer, of the solid content of aninorganic/organic silicon compound, incorporated to the aqueousdispersion.

(19)

A composition for water-based coating material, comprising the aqueousdispersion as defined in (17) and from 0.1 to 100 parts by weight, per100 parts by weight of the solid content of the composite particles, ofthe solid content of an inorganic/organic silicon compound, incorporatedto the aqueous dispersion.

(20)

A composition for water-based coating material, comprising the aqueousdispersion as defined in (17) and a hydrazine derivative having at leasttwo hydrazine residues, incorporated to the aqueous dispersion.

(21)

An aqueous dispersion characterized in that a fluorocopolymer which is acopolymer comprising (a) polymer units based on a fluoroolefin, (b)polymer units based on propylene, (c) polymer units based on ethyleneand/or (d) polymer units based on butylene, and (f) polymer units basedon a hydrophilic macro monomer represented by the general formula: X-Y-Z(wherein X is a radical polymerizable unsaturated group, Y is ahydrophobic bivalent connecting group, and Z is a hydrophilic group) andwhich has a melting point within a range of from 40 to 150° C., isdispersed in water.

(22)

An aqueous dispersion characterized in that a fluorocopolymer which isthe fluorocopolymer as defined in (21) and which has a glass transitiontemperature within a range of from −20° C. to +80° C., is dispersed inwater.

(23)

An aqueous dispersion characterized in that a fluorocopolymer which isthe fluorocopolymer as defined in (21) and which has a value Q as anindex of its molecular weight within a range of from 0.1 to 10,000, isdispersed in water, provided that the value Q is a value defined by avolume extruded in a unit time (mm³/sec), when, using a flow tester, thefluorocopolymer is filled in a cylinder having an inner diameter of 11.3mm and then extruded from a nozzle having an inner diameter of 2.1 mmand a length of 8 mm under a load of 7 kg at 140° C.

(24)

An aqueous dispersion characterized in that a fluorocopolymer which isthe fluorocopolymer as defined in (21) and which has a particle sizewithin a range of from 50 nm to 300 nm, is dispersed in water.

(25)

An aqueous dispersion characterized in that a fluorocopolymer which isthe fluorocopolymer as defined in (21) and which has a content offluorine atoms within a range of from 20 to 65 wt %, is dispersed inwater.

(26)

An aqueous dispersion obtained by emulsion polymerization, in thepresence of 100 parts by weight of particles of the fluorocopolymer asdefined in any one of (21) to (25), of from 100 to 10,000 parts byweight of a mixture of the same combination of monomers as for saidparticles.

(27)

An aqueous dispersion characterized in that composite particles obtainedby emulsion polymerization of from 5 to 200 parts by weight of a radicalpolymerizable monomer mixture comprising, as the main component, analkyl (meth)acrylate having a C₁₋₈ alkyl group, in the presence of 100parts by weight of particles of the fluorocopolymer as defined in anyone of (21) to (26), are dispersed in water.

(28)

A composition for water-based coating material, comprising the aqueousdispersion of the fluorocopolymer as defined in any one of (21) to (26)and from 0.1 to 100 parts by weight, per 100 parts by weight of thesolid content of the fluorocopolymer, of the solid content of aninorganic/organic silicon compound, incorporated to the aqueousdispersion.

(29)

A composition for water-based coating material, comprising the aqueousdispersion as defined in (27) and from 0.1 to 100 parts by weight, per100 parts by weight of the solid content of the composite particles, ofthe solid content of an inorganic/organic silicon compound, incorporatedto the aqueous dispersion.

(30)

A composition for water-based coating material, comprising the aqueousdispersion as defined in (27) and a hydrazine derivative having at leasttwo hydrazine residues, incorporated to the aqueous dispersion.

(31)

An aqueous dispersion characterized in that a fluorocopolymer which is acopolymer comprising (a) polymer units based on a fluoroolefin, (b)polymer units based on propylene, (c) polymer units based on ethyleneand/or (d) polymer units based on butylene, (e) polymer units of atleast one member selected from a vinyl ester, a vinyl ether, anisopropenyl ether and an allyl ether, and (f) polymer units based on ahydrophilic macro monomer represented by the general formula: X-Y-Z(wherein X is a radical polymerizable unsaturated group, Y is ahydrophobic bivalent connecting group, and Z is a hydrophilic group) andwhich has a melting point within a range of from 40 to 150° C., isdispersed in water.

(32)

An aqueous dispersion characterized in that a fluorocopolymer which isthe fluorocopolymer as defined in (31) and which has a glass transitiontemperature within a range of from −20° C. to +80° C., is dispersed inwater.

(33)

An aqueous dispersion characterized in that a fluorocopolymer which isthe fluorocopolymer as defined in (31) and which has a value Q as anindex of its molecular weight within a range of from 0.1 to 10,000, isdispersed in water, provided that the value Q is a value defined by avolume extruded in a unit time (mm³/sec), when, using a flow tester, thefluorocopolymer is filled in a cylinder having an inner diameter of 11.3mm and then extruded from a nozzle having an inner diameter of 2.1 mmand a length of 8 mm under a load of 7 kg at 140° C.

(34)

An aqueous dispersion characterized in that a fluorocopolymer which isthe fluorocopolymer as defined in (31) and which has a particle sizewithin a range of from 50 nm to 300 nm, is dispersed in water.

(35)

An aqueous dispersion characterized in that a fluorocopolymer which isthe fluorocopolymer as defined in (31) and which has a content offluorine atoms within a range of from 20 to 65 wt %, is dispersed inwater.

(36)

An aqueous dispersion obtained by emulsion polymerization, in thepresence of 100 parts by weight of particles of the fluorocopolymer asdefined in any one of (31) to (35), of from 100 to 10,000 parts byweight of a mixture of the same combination of monomers as for saidparticles.

(37)

An aqueous dispersion characterized in that composite particles obtainedby emulsion polymerization of from 5 to 200 parts by weight of a radicalpolymerizable monomer mixture comprising, as the main component, analkyl (meth)acrylate having a C₁₋₁₈ alkyl group, in the presence of 100parts by weight of particles of the fluorocopolymer as defined in anyone of (31) to (36), are dispersed in water.

(38)

A composition for water-based coating material, comprising the aqueousdispersion of the fluorocopolymer as defined in any one of (31) to (36)and from 0.1 to 100 parts by weight, per 100 parts by weight of thesolid content of the fluorocopolymer, of the solid content of aninorganic/organic silicon compound, incorporated to the aqueousdispersion.

(39)

A composition for water-based coating material, comprising the aqueousdispersion as defined in (37) and from 0.1 to 100 parts by weight, per100 parts by weight of the solid content of the composite particles, ofthe solid content of an inorganic/organic silicon compound, incorporatedto the aqueous dispersion.

(40)

A composition for water-based coating material, comprising the aqueousdispersion as defined in (37) and a hydrazine derivative having at leasttwo hydrazine residues, incorporated to the aqueous dispersion.

(41)

A composition for water-based coating material, comprising an aqueousdispersion of a fluorocopolymer obtained by emulsion polymerization offrom 5 to 100 parts by weight of a radical polymerizable monomer mixturecomprising (j) a monomer comprising, as the main component, an alkyl(meth)acrylate having a C₁₋₁₈ alkyl group and (k) a carbonylgroup-containing monomer, in the presence of 100 parts by weight ofparticles of the fluorocopolymer as defined in any one of (1) to (6),and a hydrazine derivative containing at least two hydrazine residues,incorporated to the aqueous dispersion.

(42)

A composition for water-based coating material, comprising an aqueousdispersion of a fluorocopolymer obtained by emulsion polymerization offrom 5 to 100 parts by weight of a radical polymerizable monomer mixturecomprising (j) a monomer comprising, as the main component, an alkyl(meth)acrylate having a C₁₋₁₈ alkyl group and (k) a carbonylgroup-containing monomer, in the presence of 100 parts by weight ofparticles of the fluorocopolymer as defined in any one of (11) to (16),and a hydrazine derivative containing at least two hydrazine residues,incorporated to the aqueous dispersion.

(43)

A composition for water-based coating material, comprising an aqueousdispersion of a fluorocopolymer obtained by emulsion polymerization offrom 5 to 100 parts by weight of a radical polymerizable monomer mixturecomprising (j) a monomer comprising, as the main component, an alkyl(meth)acrylate having a C₁₋₁₈ alkyl group and (k) a carbonylgroup-containing monomer, in the presence of 100 parts by weight ofparticles of the fluorocopolymer as defined in any one of (21) to (26),and a hydrazine derivative containing at least two hydrazine residues,incorporated to the aqueous dispersion.

(44)

A composition for water-based coating material, comprising an aqueousdispersion of a fluorocopolymer obtained by emulsion polymerization offrom 5 to 100 parts by weight of a radical polymerizable monomer mixturecomprising (j) a monomer comprising, as the main component, an alkyl(meth)acrylate having a C₁₋₁₈ alkyl group and (k) a carbonylgroup-containing monomer, in the presence of 100 parts by weight ofparticles of the fluorocopolymer as defined in any one of (31) to (36),and a hydrazine derivative containing at least two hydrazine residues,incorporated to the aqueous dispersion.

BEST MODE FOR CARRYING OUT THE INVENTION

In the present invention, an aqueous dispersion of a fluorocopolymercomprising (a) polymer units based on a fluoroolefin, (b) polymer unitsbased on propylene, as essential components, and further (c) polymerunits based on ethylene and/or (d) polymer units based on butylene, isused.

Here, the fluorocopolymer is preferably composed of the followingcompositional proportions of the polymer units based on the followingmonomers (hereinafter represented by the monomer names).

(a) fluoroolefin 20 to 80 mol% (b) propylene 2 to 70 mol% (c) ethylene(5) to (70) mol% (d) butylene (5) to (70) mol%.

The compositional proportions are further preferably:

(a) fluoroolefin 35 to 65 mol% (b) propylene 4 to 55 mol% (c) ethylene(8) to (60) mol% (d) butylene (8) to (60) mol%.

Most preferably:

(a) fluoroolefin 40 to 60 mol% (b) propylene 6 to 35 mol% (c) ethylene(10) to (35) mol% (d) butylene (10) to (35) mol%.

Here, the compositional proportions of the polymer units (c) ethyleneand (d) butylene are bracketed and represented, for example, as (5), (8)and (10), for the following meanings. Namely, as defined in the Claims,at least one of (c) and (d) is necessarily contained, and the other maynot be contained at all, and (5), (8), (10) or the like represents thecontent of the component (c) or (d) thus contained alone in such a case.Further, when both (c) and (d) are contained, (5), (8), (10) or the likerepresents the total content of both components.

When the fluorocopolymer of the present invention is employed for acoating material, if the proportion of the fluoroolefin polymer units(a) is to small, the weather resistance tends to be poor, and if it istoo large, the cost tends to be high relative to the improvement inweather resistance, such being undesirable. Taking these intoconsideration, the above range is selected.

Further, if the proportion of the polymer units (b) is too small, thefluorocopolymer tends to be rubbery, and the hardness of the coatingfilm tends to be inadequate, and if it is too large, the melting pointtends to be too high, and the flexibility of the coating film tends tobe inadequate. Taking these into consideration, the above range isselected.

As mentioned above, the polymer units (c) and (d) may both be usedtogether, or either one may be used. However, it is essential to use atleast one of them. If the proportion of (c) and/or (d) is too small, themelting point tends to be too high, and the crystallization of thecoating film tends to be high, whereby the transparency tends todecrease. If it is too large, the fluorocopolymer tends to be rubbery,whereby the hardness tends to be inadequate. Taking these intoconsideration, the above range is selected as preferred.

In the present invention, the fluoroolefin is preferably a C₂₋₄fluoroolefin containing fluorine atoms, such as trifluoroethylene,chlorotrifluoroethylene, tetrafluoroethylene, trifluoropropylene,tetrafluoropropylene, pentafluoropropylene, hexafluoropropylene,tetrafluorobutylene or pentafluorobutylene, particularly preferably aperfluoroolefin. Most preferably, it is tetraf luoroethylene. Further,it may contain, in addition to fluorine atoms, other halogen atoms suchas chlorine atoms.

Further, as the butylene in the present invention, 1-butylene,2-butylene and isobutylene may be used. From the viewpoint of easyavailability, isobutylene is most preferred. Further, a mixture of themmay be employed.

The range of the melting point of the fluorocopolymer of the presentinvention is from 40 to 150° C., preferably from 60 to 120° C. If themelting point is too low, the hardness of the coating film tends to beinadequate, and if the melting point is too high, no adequate fluidityis obtainable at the time of heat coating, whereby the appearance of thecoating film will be impaired. Whereas, in the case of a vinylidenefluoride type resin, even in the same melting point range, the hardnessof the coating film is likely to be inadequate, or the transparency islikely to be low due to high crystallizability.

The range of the glass transition temperature of the fluorocopolymer ofthe present invention is from −20° C. to +80° C., preferably from 0 to70° C. If the glass transition temperature is too low, the hardness ofthe coating film tends to be inadequate, and if it is too high, noadequate fluidity is obtainable at the time of heat coating, whereby theappearance of the coating film will be impaired. Whereas, in the case ofa vinylidene fluoride type resin, the glass transition temperature islow, and the hardness of the coating film will be inadequate.

For the melting point and the glass transition temperature, a sample washeated at a rate of 10° C./min by a differential scanning calorimeter(DSC), whereby the heat generation peak was obtained, and thetemperature at that time was taken as the melting point. In a case wherethe distribution of the peak of the melting point was wide, the lowestpoint of the portion downwardly projected was taken as the meltingpoint.

It is important that the value Q as an index of the molecular weight ofthe fluorocopolymer of the present invention is within a range of from0.1 to 10,000, more preferably from 1 to 1,000, still further preferablyfrom 10 to 500.

If the value Q is less than 0.1, the fluidity of particles tends to below, whereby the film-forming properties and smoothness of the coatingfilm tend to deteriorate. If it is larger than 10,000, the mechanicalstrength of the coating film tends to be impaired.

The range of the particle size of the fluorocopolymer of the presentinvention is from 50 nm to 300 nm, preferably from 70 to 200 nm.

Here, the particle size is an average particle size measured by means ofa laser beam scattering particle size measuring apparatus (ELS-3000,manufactured by Otsuka Denshi K.K.).

If the particle size is less than 50 nm, the mechanical stability tendsto deteriorate, and the film-forming properties also tend todeteriorate. If it exceeds 300 nm, the precipitation stability, thethermal stability, the mechanical stability and the chemical stabilitytend to be impaired. However, particles having particle sizes other thanthe above range may be contained if they are less than 10 wt %.

The content of fluorine atoms in the fluorocopolymer of the presentinvention is within a range of from 20 to 65 wt %, preferably from 30 to60 wt %. If the content of fluorine atoms is too small, the weatherresistance tends to deteriorate, and if it is too large, the adhesion ofthe coating film to the substrate tends to deteriorate.

The fluorocopolymer of the present invention may be a copolymercontaining, in addition to the polymer units based on monomers for theabove (a) to (d), (e) polymer units based on at least one monomerselected from a vinyl ester, a vinyl ether, an isopropenyl ether and anallyl ether. If the polymer units based on such a monomer are contained,not only the pigment dispersibility and adhesion to the substrate willbe improved, but also affinity to an acrylic monomer will be improved,whereby the transparency and weather resistance of the coating film willbe improved.

If the polymer units based on the above-mentioned (e) at least onemonomer selected from a vinyl ester, a vinyl ether, an isopropenyl etherand an allyl ether are too much, the coating film tends to be tacky.Further, if they are too little, no adequate effects for improvement inpigment dispersibility, adhesion to the substrate and the affinity to anacrylic monomer, can be obtained.

Accordingly, the content of polymer units based on component (e) ispreferably at a level of from 5 to 20 mol %.

The above vinyl ester may, for example, be vinyl acetate, vinylpropionate, vinyl butyrate, vinyl pivalate, vinyl capronate, vinylcaprylate or vinyl stearate. The vinyl ether may, for example, be methylvinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether orcyclohexyl vinyl ether. The isopropenyl ether may, for example, bemethyl isopropenyl ether, ethyl isopropenyl ether, propyl isopropenylether, butyl isopropenyl ether or cyclohexyl isopropenyl ether. Theallyl ether may, for example, be ethyl allyl ether, propyl allyl ether,butyl allyl ether or isobutyl allyl ether.

Further, the polymer units based on the monomer of the above (e) maycontain a reactive group selected from a hydroxyl group, a carboxylicacid group, an epoxy group and a hydrolysable silyl group. The polymerunits based on the monomer containing such a reactive group may beincorporated in an amount of at least 20 mol %, preferably at least 25mol %, in the polymer units based on the monomer of the above (e).

Even when the fluorocopolymer of the present invention has such reactivegroups, the stability of the dispersion will not be impaired. And, in acase where the fluorocopolymer has such reactive groups, there is amerit in that by using a curing agent when such aqueous dispersion isused as the base for coating material, it is possible to form a coatingfilm having excellent water resistance and solvent resistance uponcrosslinking. In this sense, such reactive groups may be regarded ascorresponding to cure sites.

Polymer units containing hydroxyl groups may be introduced by a methodof copolymerizing such a hydroxyl group-containing monomer or by amethod of forming hydroxyl group-containing units by subjecting thepolymer to a high molecular reaction.

Here, the hydroxyl group-containing monomer may, for example, be ahydroxyalkyl vinyl ether such as hydroxybutyl vinyl ether (HBVE); ahydroxyalkyl allyl ether such as hydroxyethyl allyl ether; ahydroxyalkyl ester of acrylic acid or methacrylic acid, such ashydroxyethyl acrylate or hydroxyethyl methacrylate.

Further, the method of forming polymer units containing hydroxyl groupsby subjecting a polymer to a high molecular reaction, may, for example,be a method wherein after the polymerization, a hydrolysable vinyl esteris copolymerized, followed by hydrolysis to form hydroxyl groups.

On the other hand, polymer units containing carboxylic acid groups maybe introduced by a method of copolymerizing a carboxylic acidgroup-containing monomer or by a method of forming carboxylic acidgroups by reacting a dibasic acid anhydride to a polymer having hydroxylgroups.

Here, the carboxylic acid group-containing monomer may, for example, beas follows.

CH₂═CHOR¹COR²COOM  (A)

 CH₂═CHCH₂R³COR⁴COOM  (B)

(wherein each of R¹ and R³ is a C₂₋₁₅ bivalent hydrocarbon group, eachof R² and R⁴ is a saturated or unsaturated linear or cyclic bivalenthydrocarbon group, and M is a hydrogen atom, a hydrocarbon group, analkali metal ion or a compound containing a nitrogen atom).

Polymer units containing epoxy groups can be introduced bycopolymerizing a monomer containing an epoxy group. The monomercontaining an epoxy group may, for example, be an epoxy group-containingalkyl vinyl ether such as glycidyl vinyl ether; an epoxygroup-containing alkyl allyl ether such as glycidyl allyl ether; or anepoxy group-containing alkyl acrylate or methacrylate, such as glycidylacrylate or glycidyl methacrylate.

The polymer units containing hydrolysable silyl groups may be introducedby copolymerizing a monomer containing a hydrolysable silyl group. Themonomer containing a hydrolysable silyl group may, for example, betrimethoxy vinyl silane or triethoxy vinyl silane.

In the fluorocopolymer of the present invention, in addition to monomersof the above (a) to (d) or the above (a) to (e), (f) a hydrophilic macromonomer represented by the general formula: X-Y-Z (wherein X is aradical polymerizable unsaturated group, Y is a hydrophobic bivalentconnecting group, and Z is a hydrophilic group), may be copolymerized.If the polymer units based on such a hydrophilic macro monomer, arecontained, not only the mechanical stability and the chemical stabilityof the aqueous dispersion will be improved, but also the film-formingproperties and the mechanical strength of the coating film will beexcellent, and further an emulsifier for stabilization is not totally orsubstantially required, whereby the water resistance or stain resistancecan be improved.

Here, the radical polymerizable unsaturated group X may, for example, bea vinyl group (CH₂═CH—), an allyl group (CH₂═CHCH₂—), a propenyl group(CH₃CH═CH—), an isopropenyl group (CH₂═C(CH₃)—), an acryloyl group(CH₂═CHCO—) or a methacryloyl group (CH₂═C(CH₃)CO—).

The hydrophobic bivalent connecting group Y may, for example, bepreferably a linear or branched hydrocarbon group, a polyoxypropylenegroup, an alicyclic group such as a cyclohexane ring or a cyclododecanering, and an aromatic group. The more hydrophobic the connecting group,the higher the compatibility of the hydrophilic macro monomer with othercopolymerizable monomer such as ethylene and propylene, whereby thereactivity of the macro monomer will be improved, and consequently, itbecomes possible to obtain an aqueous dispersion of a fluorocopolymerexcellent in stability even if an emulsifier for stabilization is nottotally or substantially used.

The hydrophilic group Z may be ionic, nonionic, amphoteric, or acombination thereof. When it is composed solely of an ionic hydrophilicgroup, the chemical stability of the aqueous dispersion of thefluorocopolymer tends to decrease, and it is preferred to combine amacro monomer having a nonionic or amphoteric hydrophilic group. Fromthe viewpoint of the intensity of the hydrophilicity or the influenceover the coating film properties, a nonionic hydrophilic group such as apolyoxyethylene group or a polyoxypropylene/polyoxyethylene group, isparticularly preferred.

The macro monomer is meant for a low molecular weight polymer or anoligomer having a radical polymerizable unsaturated group at oneterminal. Namely, it is a compound having a radical polymerizableunsaturated group at one terminal and at least two repeating units inorder to obtain adequate stability. Usually, one having at most 100repeating units, is preferably employed from the viewpoint of thepolymerizability and water resistance, although such may vary dependingupon the type of the repeating units.

As the hydrophilic macro monomer, one with one terminal being a vinylether type or an allyl ether type, is preferred.

For example, it may be:

CH₂═CHOCH₂-cyclo-C₆H₁₀—CH₂O(CH₂CH₂O)_(t)X  (D)

(wherein t is an integer of from 2 to 40, and X is a hydrogen atom, alower alkyl group or a lower acyl group).

CH₂═CHO—C₄H₈—O—(CH₂CH (CH₃)O)_(u)—CH₂O(CH₂CH₂O)_(t)X  (E)

(wherein u is an integer of from 1 to 10, and t and X are as definedabove).

CH₂═CHO—C₄H₈—O—(CH₂CH₂O)_(t)X  (F)

(wherein t and X are as defined above).

CH₂═CHCH₂O—C₄H₈—O—(CH₂CH(CH₃)O)_(u)—CH₂O(CH₂CH₂O)_(t)X  (G)

(wherein u, t and X are as defined above).

Further, the connecting moiety of (—cyclo-C₆H₁₀—) is 1,4-, 1,3- or 1,2-.However, usually, 1,4- is employed.

Especially one having a vinyl ether type structure at one terminal ispreferred since it is excellent in alternate copolymerizability with afluoroolefin, and the weather resistance of the copolymer coating filmwill be good. The following may, for example, be mentioned.

CH₂═CHO—C₄C₈—O—(CH₂CH₂O)_(n)H  (Q)

CH₂═CHOCH₂-cyclo-C₆H₁₀—CH₂O—(CH₂CH₂O)_(n)H  (V)

CH₂═CHO-cyclo-C₆H₁₀—C(CH₃)₂-cyclo-C₆H₁₀—O—(CH₂CH₂O)_(n)H  (W)

In the above (Q), (V) and (W), n is an integer of from 2 to 40.

Such a hydrophilic macro monomer can be produced by a method ofpolymerizing formaldehyde to an alkyl allyl ether or an alkyl vinylether having a hydroxyl group, or subjecting an alkylene oxide or acompound having a lactone ring to ring opening polymerization. It canalso be produced by introducing vinyl ether groups or allyl ether groupsto a terminal of a hydrophilic polymer such as polyethylene glycol.

Further, the hydrophilic macro monomer may be a macro monomer which hasa chain having a hydrophilic ethylenic unsaturated monomerradical-polymerized and which has a radical polymerizable unsaturatedgroup such as a vinyl ether or an allyl ether at its terminal. Such amacro monomer can be produced, for example, by a method disclosed byYamashita et al. in Polym. Bull., 5. 335 (1981)). Namely, an ethylenicunsaturated monomer having a hydrophilic group is radical-polymerized inthe presence of a chain transfer agent and an initiator having acondensable functional group to produce a polymer having condensablefunctional groups, and then a compound such as glycidyl vinyl ether orglycidyl allyl ether, is reacted to such functional groups of thispolymer, to introduce radical polymerizable unsaturated groups at theterminal.

The ethylenic unsaturated monomer to be used for the production of thishydrophilic macro monomer, may, for example, be acrylamide,methacrylamide, N-methylol acrylamide, N-methylol methacrylamide,2-methoxyethyl acrylate, 2-methoxyethyl methacrylate, diacetoneacrylamide, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutylacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate,hydroxybutyl methacrylate, an acrylate of a polyhydric alcohol, amethacrylate of a polyhydric alcohol, and vinyl pyrrolidone.

Other than these, a monomer copolymerizable with an ethylenicunsaturated monomer may be used together with the ethylenic unsaturatedmonomer. As such a copolymerizable monomer, acrylamide or itsderivative, methacrylamide or its derivative, an N-methylol acrylamidederivative, diethylene glycol monoethyl ether monoacrylate, triethyleneglycol monomethyl ether monoacrylate, a phosphate of 2-hydroxyethylacrylate, or butoxyethyl acrylate, may be mentioned.

Further, the initiator to be used for the production of such ahydrophilic macro monomer, may, for example, be4,4′-azobis-4-cyanovalerianic acid, 2,2′-azobis-2-amidinopropanehydrochloride, potassium persulfate, ammonium persulfate,azobisisobutyronitrile or benzoyl peroxide.

It is preferred that in the fluorocopolymer of the present invention,the polymer units based on the hydrophilic macro monomer are containedin a proportion of from 0.1 to 25 mol %, preferably from 0.3 to 20 mol%. If the content of the polymer units based on the hydrophilic macromonomer is too small, the mechanical stability and the chemicalstability of the aqueous dispersion can not remarkably be improved, andif it is too large, the weather resistance and the water resistance ofthe coating film tend to be poor, such being undesirable.

The aqueous dispersion of the present invention is one having thefluorocopolymer dispersed in water. Further, the aqueous dispersion ofthe present invention is excellent in the dispersion stability even ifan emulsifier which is commonly employed for an aqueous dispersion of afluorocopolymer, is not employed. However, use of an emulsifier is notexcluded. As the emulsifier, nonionic emulsifiers and anionicemulsifiers may be employed alone or in combination. The nonionicemulsifiers may, for example, be an alkylphenol ethylene oxide adduct, ahigher alcohol ethylene oxide adduct, and a block copolymer of ethyleneoxide with propylene oxide. The anionic emulsifiers may, for example, bean alkylbenzene sulfonate, an alkylnaphthalene sulfonate, a higher fattyacid salt, an alkylsulfonic acid ester salt, an alkyl ether sulfonicacid ester salt, a phosphoric acid ester salt.

Further, such an emulsifier is used usually by adding it duringpolymerization, but an emulsifier of the same type and/or an emulsifierof a different type may be added to the aqueous dispersion after thepolymerization.

Here, as the emulsifier to be added to the aqueous dispersion after thepolymerization, in addition to the above-mentioned emulsifiers, analkali metal salt of a dialkyl sulfosuccinic acid such as sodium dioctylsulfosuccinate or sodium dinonyl sulfosuccinate, and a combinationthereof with an alkylene glycol such as ethylene glycol or propyleneglycol, may, for example, be mentioned. When such an alkali metal saltof a dialkyl sulfosuccinic acid and an alkylene glycol are added, themechanical stability and the thermal stability of the above aqueousdispersion can be improved.

Initiation of the emulsion polymerization in the present invention iscarried out by addition of a polymerization initiator in the same manneras the initiation of usual emulsion polymerization. As thepolymerization initiator, a usual radical initiator may be employed, buta water-soluble initiator is particularly preferably employed.Specifically, a persulfate such as ammonium persulfate, hydrogenperoxide, or a redox initiator composed of a combination thereof with areducing agent such as sodium hydrogen sulfite or sodium thiosulfate, aninorganic initiator of a system having a small amount of iron, a ferroussalt, silver sulfate or the like incorporated thereto, or an organicinitiator such as a dibasic acid peroxide such as disuccinic acidperoxide or diglutaric acid peroxide, azobisisobutylamidinehydrochloride or azobisisobutyronitrile, may, for example, be mentioned.

The amount of the polymerization initiator can be changed optionallydepending upon the type and the emulsion polymerization conditions, butit is usually at a level of from 0.005 to 0.5 part by weight, per 100parts by weight of the monomer to be subjected to emulsionpolymerization. Further, such a polymerization initiator may be addedall at once or dividedly as the case requires.

Further, a pH controlling agent may be used for the purpose ofincreasing the pH of the emulsion. As such a pH controlling agent, aninorganic base such as sodium carbonate, potassium carbonate, sodiumhydrogen orthophosphate, sodium thiosulfate or sodium tetraborate, or anorganic base such as triethylamine, triethanolamine,dimethylethanolamine or diethylethanolamine, may, for example, bementioned.

The amount of the pH controlling agent is usually at a level of from0.05 to 2 parts by weight, preferably from 0.1 to 2 parts by weight, per100 parts by weight of the emulsion polymerization medium. The higherthe pH is, the higher the polymerization rate tends to be.

Further, with respect to the initiation temperature for the emulsionpolymerization, an optimum value is suitably selected depending upon thetype of the polymerization initiator. However, usually, a temperature offrom 0 to 100° C., particularly from about 10 to 90° C., is preferablyemployed. The polymerization temperature is from about 20 to 120° C.Further, the reaction pressure can be optionally selected, but usually,it is preferred to employ a pressure of from 0.1 to 10 MPa, particularlyfrom about 0.2 to 5 MPa.

In such a production method, the additives such as the monomer, water,the emulsifier and the polymerization initiator may be charged all atonce for polymerization. However, for the purpose of improving variousphysical properties such as the stability of the dispersion and thegloss of the coating film by reducing the particle size of dispersedparticles, preliminary emulsifying may be carried out by means of astirrer such as a homogenizer prior to addition of the polymerizationinitiator, and then the initiator is added for polymerization. Further,various methods may be employed, such as a method of introducing themonomer in its entire amount all at once into the reactor, a method ofintroducing the entire amount of the monomer continuously, a method ofintroducing the monomer by dividing its entire amount, and a method ofcharging a part of the monomer for preliminary reaction and thenintroducing the rest dividedly or continuously. Further, in the case ofdivided addition, the monomer composition may be different.

The fluorocopolymer of the present invention may be prepared by emulsionpolymerization, in the presence of particles of the fluorocopolymerpreliminarily polymerized, of a monomer having the same monomercomposition as the particles. By the presence of the copolymer particlesin water preliminarily, the gaseous monomer tends to be readilyabsorbed, whereby the polymerization rate will be improved. Further, atthat time, the particles of the preliminarily polymerizedfluorocopolymer may be diluted and then the emulsion polymerization iscarried out, whereby the stability of the dispersion can further beimproved.

In such a case, it is preferred to carry out the polymerization in aratio of from 100 to 10,000 parts by weight of the monomer mixture, per100 parts by weight of the particles of the fluorocopolymerpreliminarily charged at the time of the polymerization. If theproportion of the particles of the fluorocopolymer preliminarilycharged, is too low, the effect for the improvement of thepolymerization rate tends to be small, and if it is too high, the yieldof an aqueous dispersion obtainable by a single polymerization operationtends to be small, such being not economical.

Further, in order to further improve the absorption of the gas of themonomer, a hydrophilic organic compound, such as an alcohol such asmethanol, ethanol, isopropanol, n-butanol, isobutanol or t-butanol; oran alkylene glycol such as ethylene glycol or propylene glycol, may beadded at the time of the polymerization. In this case, the amount ofaddition is preferably from 0.1 to 10 wt %, based on water of theaqueous dispersion. More preferably, it is from 1 to 5 wt %. If theamount of addition is smaller than this, the gas absorbing effect tendsto be small, and if it is too large, the content of a volatile organiccompound tends to be large, whereby the environment will be adverselyaffected.

Further, in the aqueous dispersion having the above-mentionedfluorocopolymer dispersed therein, a radical polymerizable monomercomprising, as the main component, a monomer of an alkyl (meth)acrylate(hereinafter referred to also as a (meth)acrylate), can be subjected toemulsion polymerization. Such emulsion polymerization of a radicalpolymerizable monomer comprising, as the main component, a monomer of a(meth)acrylate, in the aqueous dispersion having the fluorocopolymerdispersed therein, is one which should be referred to as a post reactionagainst the dispersed fluorocopolymer or so-called seed polymerizationusing it as seed particles. In the process of the emulsionpolymerization, some mutual actions take place such as penetration ofthe radical polymerizable monomer comprising, as the main component, amonomer of a (meth)acrylate, into the fluorocopolymer and swelling, andas a result, as the aqueous dispersion of the finally obtainablefluorocopolymer, it is expected to obtain one having the fluorocopolymerand the copolymer comprising, as the main component, a monomer of a(meth)acrylate, mutually more uniformly dispersed as compared with oneobtained by preparing the two dispersions separately and then mixingthem.

By subjecting the radical polymerizable monomer comprising, as the maincomponent, a monomer of a (meth)acrylate, to seed polymerization, it ispossible to improve the mechanical stability, the chemical stability,the film-forming properties, the pigment dispersibility and theprocessability, while maintaining the characteristics such as theweather resistance of the fluorocopolymer.

Here, the (meth)acrylate is preferably one wherein the carbon number ofthe alkyl group is from 1 to 18, and for example, methyl (meth)acrylate,ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate,isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-amyl (meth)acrylate,isoamyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate,2-ethylhexyl (meth)acrylate, or lauryl (meth)acrylate, may, for example,be mentioned. Among them, a (meth)acrylate having a C₁₋₅ alkyl group, isparticularly preferred.

Further, together with the above-mentioned (meth)acrylate, other monomercopolymerizable therewith may be used within a range of not more than 50mol %, preferably not more than 30 mol %, based on the above-mentioned(meth)acrylate.

Other monomer copolymerizable with the (meth)acrylate may, for example,be a carboxyl group-containing monomer such as (meth)acrylic acid,maleic acid or crotonic acid; an amide compound such as(meth)acrylamide, N-methyl (meth)acrylamide, N-methylol (meth)acrylamideor N-butoxymethyl (meth)acrylamide; a hydroxyl group-containing monomersuch as hydroxyethyl (meth)acrylate, or hydroxypropyl (meth)acrylate; anepoxy group-containing monomer such as glycidyl (meth)acrylate; or ahydrolysable silyl group-containing monomer such as γ-trimethoxysilane(meth)acrylate or γ-triethoxysilane (meth)acrylate.

In a case where the monomer comprising, as the main component, a(meth)acrylate is subjected to emulsion polymerization in an aqueousdispersion of the present invention, it is preferred that from 5 to 200parts by weight of a radical polymerizable monomer mixture comprising,as the main component, an alkyl (meth)acrylate having a C₁₋₁₈ alkylgroup is subjected to emulsion polymerization in the presence of 100parts by weight of particles of the fluorocopolymer. In a case wheretogether with the (meth)acrylate, other monomer copolymerizabletherewith is subjected to emulsion polymerization, it is preferred thatfrom 5 to 200 parts by weight of a mixture comprising an alkyl(meth)acrylate having a C₁₋₁₈ alkyl group and a radical polymerizableother monomer having a functional group selected from a carboxyl group,a hydrolysable silyl group, an epoxy group and a hydroxyl group, issubjected to emulsion polymerization in the presence of 100 parts byweight of particles of the fluorocopolymer. Accordingly, in a case wherethe above-mentioned so-called seed polymerization is employed, from 5 to200 parts by weight of a monomer comprising, as the main component, the(meth)acrylate, is charged into a reactor and subjected to emulsionpolymerization in the presence of 100 parts by weight of particles ofthe fluorocopolymer.

The conditions for the emulsion polymerization of the monomercomprising, as the main component, the above (meth)acrylate, may be inaccordance with the conditions employed for the emulsion polymerizationrelating to the above described fluorocopolymer.

By the above method, an aqueous dispersion containing thefluorocopolymer and a copolymer comprising, as the main component, the(meth)acrylate, can be obtained, and the content of the copolymercomprising, as the main component, the (meth)acrylate is from 5 to 200parts by weight, preferably from 10 to 100 parts by weight, morepreferably from 20 to 50 parts by weight, per 100 parts by weight of thefluorocopolymer. The range of the melting point of the compositeparticles comprising the fluorocopolymer and the copolymer comprising,as the main component, the (meth)acrylate, is preferably from 40 to 150°C., more preferably from 60 to 120° C. If the melting point is too low,the hardness of the coating film tends to be inadequate, and if themelting point is too high, no adequate fluidity can be obtained at thetime of heat coating, and the appearance of the coating film tends to beimpaired.

To obtain a crosslinkable composition for water-based coating material,firstly, from 5 to 100 parts by weight of a mixture comprising (j) theabove-mentioned (meth)acrylate having a C₁₋₁₈ alkyl group and/or othermonomer copolymerizable therewith, and (k) a radical polymerizablemonomer composed of a carbonyl group-containing monomer, is subjected toemulsion polymerization in the presence of 100 parts by weight ofparticles of the fluorocopolymer. Then, to the aqueous dispersionthereby obtainable, a hydrazine derivative containing at least twohydrazine residues, is incorporated to obtain a composition forwater-based coating material.

The carbonyl group-containing monomer (k) may, for example, be a C₄₋₇vinyl alkyl ketone such as acrolein, diacetone acryloamide, formylstyrol or vinyl ethyl ketone, a (meth)acryloxyalkyl propanol,acetonitrile acrylate, diacetone (meth)acrylate, 2-hydroxypropyl(meth)acrylate-acetyl acetate, or butane diol 1,4-(meth)acrylate-acetylacetate. Among them, from the viewpoint of weather resistance,2-hydroxypropyl (meth)acrylate-acetyl acetate, butane diol1,4-(meth)acrylate-acetyl acetate or vinyl methyl ketone is preferred.

The above-mentioned hydrazine derivative containing at least twohydrazine residues, may, for example, be a C₂₋₁₀ carboxylic aciddihydrazide, such as oxalic acid dihydrazide, malonic acid dihydrazide,succinic acid dihydrazide, glutaric acid dihydrazide, adipic aciddihydrazide, isophthalic acid dihydrazide, sebacic acid dihydrazide,maleic acid dihydrazide, fumaric acid dihydrazide or itaconic aciddihydrazide, or a C₂₋₄ dihydrazine such as ethylene-1,2-dihydrazine,propylene-1,3-dihydrazine or butylene-1,4-dihydrazine. Among them,adipic acid dihydrazide or isophthalic acid dihydrazide is particularlypreferred.

The hydrazine derivative will react with carbonyl groups in thecopolymer to form crosslinking structures, when the above compositionfor water-based coating material is dried to form a coating film. Theratio of hydrazino groups in the hydrazine derivative to the carbonylgroups in the copolymer, is such that the hydrazino groups are from 0.5to 1.2 mol per mol of the carbonyl groups. If the hydrazino groups areless than 0.5, the crosslinking reaction tends to be inadequate, wherebythe water resistance and the solvent resistance tends to be inadequate.On the other hand, if they exceed 1.2 mol, the residual hydrazinederivative which is not concerned with the reaction tends to be so muchthat the water resistance tends to deteriorate. A particularly preferredrange is from 0.1 to 1.0 mol.

The above-mentioned copolymer comprising, as the main component, the(meth)acrylate or the copolymer obtainable by emulsion polymerization offrom 5 to 100 parts by weight of a mixture comprising (j) the(meth)acrylate and other monomer copolymerizable therewith and (k) aradical polymerizable monomer composed of a carbonyl group-containingmonomer, is from 5 to 200 parts by weight, preferably from 10 to 100parts by weight, more preferably from 20 to 50 parts by weight, per 100parts by weight of the fluorocopolymer. Accordingly, when theabove-mentioned so-called seed polymerization is employed, from 5 to 200parts by weight of a monomer mixture comprising, as the main component,the (meth)acrylic acid, or from 5 to 100 parts by weight of a mixturecomprising (j) the (meth)acrylate and other monomer copolymerizabletherewith and (k) a radical polymerizable monomer composed of a carbonylgroup-containing monomer, is charged into the reactor and subjected toemulsion polymerization in the presence of 100 parts by weight of thefluorocopolymer. Conditions for such an emulsion polymerization may bein accordance with the above described conditions for the emulsionpolymerization relating to the fluorocopolymer.

The range of the melting point of the composite particles obtained byemulsion polymerization of the monomer mixture comprising, as the maincomponent, the (meth)acrylate in the presence of the fluorocopolymer, orthe composite particles obtainable by emulsion polymerization of from 5to 100 parts by weight of a mixture comprising (j) the (meth)acrylateand other monomer copolymerizable therewith, and (k) a radicalpolymerizable monomer composed of a carbonyl group-containing monomer,in the presence of the fluorocopolymer, is required to be from 40 to150° C., more preferably from 60 to 120° C. If the melting point is toolow, the hardness of the coating film tends to be inadequate, and if themelting point is too high, no adequate fluidity will be obtained at thetime of heat coating, whereby the appearance of the coating film will beimpaired.

Further, the glass transition temperature of the above-mentionedcomposite particles is preferably within a range of from −20 to +80° C.,more preferably from 0 to 70° C. If the glass transition temperature istoo low, the coating film tends to be tacky, and if it is too high, theflexibility of the coating film tends to be impaired.

Further, the value Q as an index of the molecular weight of theabove-mentioned composite particles is preferably within a range of from0.1 to 10,000, more preferably from 1 to 1,000, still further preferablyfrom 10 to 500.

If the value Q is less than 0.1, the fluidity of the particles tends todecrease, and the film-forming properties and the smoothness of thecoating film tend to deteriorate. If it exceeds 10,000, the mechanicalstrength of the coating film tends to be impaired.

Further, the average particle size of the above-mentioned compositeparticles is preferably within a range of from 50 nm to 300 nm, morepreferably from 70 to 200 nm. If the particle size is less than 50 nm,the mechanical stability tends to deteriorate, and the film-formingproperties also tend to deteriorate. If it exceeds 300 nm, theprecipitation stability, the thermal stability, the mechanical stabilityand the chemical stability tend to be impaired. However, particleshaving particle sizes outside the above range may be contained if theyare less than 10 wt %.

In the present invention, an inorganic/organic silicon compound may beincorporated to the aqueous dispersion of the above-mentionedfluorocopolymer for the purpose of improving flexibility in addition tothe film-forming property, the chemical resistance, the weatherresistance and the adhesion to the above-mentioned inorganic substrateor organic substrate, when made into a coating material. As such aninorganic silicon compound, a water-soluble silicate so-called waterglass or a water dispersible colloidal silica may, for example, bementioned.

As the water-soluble silicate, for example, a water-soluble silicaterepresented by the Formula (I):

M₂O.XSiO₂  (I)

(wherein M is an alkali metal, or —N(CH₂CH₂OH)₄, —N(CH₂CH₂OH)₄,—N(CH₂CH₂OH)₂ or —C(NH₂)₂NH, and X is from 0.5 to 5) may be mentioned.Such a water-soluble silicate may have or may not have water ofcrystallization.

More specifically, the aqueous solution of the water-soluble silicate ofthe Formula (I) may be an aqueous solution of e.g. an alkali metalsilicate composed of silicic acid and an alkali metal belonging to GroupIA of the Periodic Table, a tertiary ammonium silicate composed ofsilicic acid and a tertiary ammonium, a quaternary ammonium silicatecomposed of silicic acid and a quaternary ammonium, or a guanidinesilicate composed of silicic acid and guanidine. The alkali metalsilicate may, for example, be sodium silicate, potassium silicate,lithium silicate or cesium silicate; the tertiary ammonium silicate may,for example, be triethanolamine silicate; and the quaternary ammoniumsilicate may, for example, be tetramethanol ammonium silicate ortetraethanol ammonium silicate.

Further, a modified water-soluble silicate obtainable by reacting one ormore of fluorides of e.g. calcium, magnesium, zinc and zirconium, withsuch a water-soluble silicate, or a modified water-soluble silicateobtainable by reacting one or more of oxides or hydroxides of a metalbelonging to Group 2A of the Periodic Table, or zinc, zirconium,vanadium or cesium, with the above-mentioned water-soluble silicate, maybe used alone or in combination.

Among such water-soluble silicates, an alkali metal silicate such aslithium silicate or sodium silicate is preferably employed.Particularly, in the case of lithium silicate, one wherein the molarratio of SiO₂/Li₂O is from 3.0 to 25.0, preferably from 3.0 to 4.8, ispreferably employed. If the molar ratio is smaller than 3.0, the waterresistance of the obtainable coating film is likely to be low, and if itexceeds 25.0, the operation efficiency for the preparation of thecoating composition and the storage stability are likely to be low. Inthe case of sodium silicate, the weight ratio of SiO₂/Na₂O is preferablywithin a range of from 1.5 to 4.0, more preferably within a range offrom 3.0 to 4.0. If the molar ratio is smaller than 1.5, the waterresistance of the obtainable coating film is likely to be low, and if itexceeds 4.0, the operation efficiency during the preparation of thecoating composition and the storage stability are likely to be low.Further, from the viewpoint of the transparency of the coating film,lithium silicate is preferred.

The colloidal silica may, for example, be produced by removal of sodium(ion exchange method, acid decomposition method or peptization method)of water glass, and the primary particle size is from 4 to 150 nm,preferably from 5 to 50 nm. Such is usually supplied in the form of anaqueous dispersion, and can be used as it is.

The above-mentioned colloidal silica may be employed in a state wherethe aqueous dispersion is an acidic side or a basic side. As a acidicside colloidal silica, a non-stabilized silica (pH 2 to 4) commerciallyavailable by a trade name Snowtex-O or Snowtex-OL (manufactured byNissan Chemical Industries, Ltd.) can be used. On the other hand, as abasic side colloidal silica, a silica (pH 8.4 to 10) stabilized by anaddition of a very small amount of alkali metal ions, aluminum ions,ammonium ions or amine, is available, and for example, thosecommercially available by trade names Snowtex 20, Snowtex C and SnowtexN (manufactured by Nissan Chemical Industries, Ltd.), trade name RudoxHS-40, HS-30, LS, SM-30, TM, AS and AM (manufactured by DuPont, U.S.A.),trade name Nalcoak (manufactured by Nalco Chemical Company, U.S.A.), andtrade name Mitten (manufactured by Monsant Chemical Company, U.S.A.),may be mentioned. If the pH is from 6 to 8, not only the stability ofthe colloidal silica, but when made into a coating material, thestability of the coating material tends to deteriorate, and coagulationand gelation tend to result.

Further, the organic silicon compound may be a monomer represented bythe general formula (II):

R¹ _(a)Si (OR²)_(4-a)  (II)

(wherein R¹ is a non-hydrolysable group or a hydrogen atom, R2 is analkyl group, an aryl group, an alkenyl group or a hydrogen atom, and ais 0, 1 or 2).

In the above general formula (II), the non-hydrolysable group may, forexample, be an alkyl group such as methyl, ethyl or propyl, an arylgroup such as a phenyl group, a tolyl group or a mesityl group, analkenyl group such as a vinyl group or an allyl group, a haloalkyl groupsuch as a γ-chloropropyl group, an aminoalkyl group such as aγ-aminopropyl group or a γ-(2-aminoethyl)aminopropyl group, aγ-glycidoxy propyl group, an epoxy alkyl group such as aβ-(3,4-epoxycyclohexyl)ethyl group, a γ-mercaptoalkyl group, amethacryloyloxyalkyl group such as a γ-methacryloyloxypropyl group, or ahydroxyalkyl group such as a γ-hydroxypropyl group. Among thesesubstituents, preferred is an alkyl group having a carbon number of notmore than 8, more preferably a carbon number of not more than 4 and onehaving a substituent added thereto such as an aminoalkyl group, an epoxyalkyl group, a methacryloyloxyalkyl group, a hydroxyalkyl group, and aphenyl group as one of aryl groups, and a C₂₋₃ alkenyl group, from sucha viewpoint that if the carbon number of the substituent is large, thereactivity tends to be low. Further, with respect to the alkyl group,the aryl group and the alkenyl group for R², the same as R¹ applies, andparticularly preferred is an alkyl group having a carbon number of notmore than 4 from such a viewpoint that if the carbon number of thesubstituent is large, the reactivity tends to be low.

Specific examples for the above general formula (II) includetetramethoxysilane, tetraethoxysilane, tetrapropoxysilane,methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane,vinyl triethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane,γ-chloropropyltrimethoxysilane, y-aminopropyltrimethoxysilane,N-(β-aminoethyl)aminopropyltrimethoxysilane,γ-glycidoxypropyltrimethoxysilane,β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,γ-mercaptopropyltrimethoxysilane,γ-methacryloyloxypropyltrimethoxysilane andγ-hydroxypropyltrimethoxysilane. From the viewpoint of the reactivity,the film-forming property and the flexibility, methyltrimethoxysilane,phenyltrimethoxysilane or γ-methacryloyloxypropyltrimethoxysilane is,for example, preferred.

In the composition for water-based coating material of the presentinvention, the ratio of the inorganic/organic silicon compound to thefluorocopolymer is such that the inorganic/organic silicon compound iswithin a range of from 0.1 to 100 parts by weight, more preferably from1 to 50 parts by weight, per 100 parts by weight of the fluorocopolymer.If the ratio of the inorganic/organic silicon compound is smaller than0.1, the stain deposition resistance of the surface of the obtainablecoating film tends to be inadequate, and if it exceeds 100, defects suchas cracks are likely to form in the coating film due to inadequateflexibility at the time of forming a coating film or as the time passes.

The aqueous dispersion of the present invention may be useful as awater-based coating material as it is. However, additives which areusually added to water-based coating materials, such as a coloringagent, a plasticizer, an ultraviolet absorber, a leveling agent, adefoaming agent, a pigment dispersing agent, a thickener, acissing-preventive agent, an anti-skinning agent and a curing agent, maybe incorporated as the case requires. Further, a metallic pigment suchas an aluminum paste may be used. As the coloring agent, a dye, anorganic pigment or an inorganic pigment may, for example, be mentioned.As the plasticizer, a conventional one, for example, a low molecularweight plasticizer such as dioctylphthalate, or a high molecular weightplasticizer such as a vinyl polymer plasticizer or a polyester typeplasticizer, may, for example, be mentioned. As a film-forming co-agent,a polyhydric alcohol monoether such as dipropylene glycol-n-butyl ether,ethylene glycol monoethyl ether, ethylene glycol monobutyl ether ordiethylene glycol monobutyl ether, or an organic acid ester, may, forexample, be used. Further, as the curing agent, a block isocyanate suchas a hexamethylene diisocyanate trimmer, or a melamine resin such asmethylated melamine or methylol modified melamine, may, for example, beused.

Further, in order to improve the stability of the aqueous dispersion, apH controlling agent may be added.

The present invention will be described in detail with reference to thefollowing Preparation Examples and Working Examples. However, thepresent invention is by no means restricted by such Examples. Further,in the following Examples, parts means parts by weight unless otherwisespecified.

PREPARATION EXAMPLE 1

Into a stainless steel autoclave having an internal capacity of 2.5 land equipped with a stirrer, 1,100 g of deionized water, 4.75 g of afluorine type anionic emulsifier (FC-143, manufactured by Sumitomo 3MCompany), 2.2 g of a nonionic emulsifier (N-1110, manufactured by NipponNyukazai K.K.) and 46.6 g of t-butanol were charged, and deaeration by avacuum pump and pressurizing with a nitrogen gas were repeated to removeair. Then, 72 g of tetrafluoroethylene, 1.1 g of propylene and 1.4 g ofethylene were introduced into the autoclave.

When the internal temperature of the autoclave reached 70° C., thepressure was 13.4 kg/cm²G. Then, 2 cc of an aqueous solution containing25% of ammonium persulfate was added to initiate the reaction. Whilemaintaining the pressure by pressurizing as the pressure decreased,430.5 g of a gas mixture comprising 50 mol % of tetrafluoroethylene, 25mol % of ethylene and 25 mol % of propylene, was continuously added tocontinue the polymerization reaction.

Further, during the progress of the reaction, 30 cc of an aqueoussolution containing 25% of ammonium persulfate was continuously added. 8hours later, supply of the gas mixture was stopped, and the autoclavewas cooled with water to room temperature, whereupon an unreactedmonomer was purged, and the autoclave was opened to obtain an aqueousdispersion having a solid content concentration of 28.4 wt %. Theparticle size was 79 nm.

A 20% ammonium chloride aqueous solution was added to the obtainedaqueous dispersion for coagulation, followed by filtration with a glassfilter, and the contained water was removed under a reduced pressure of4 mmHg over a period of 5 hours, followed by pulverization by an impacthammer mill to obtain a powder of a fluorocopolymer. As a result of theanalysis of the composition by ¹³C-NMR, this copolymer was found tocomprise 52 mol % of polymer units based on tetrafluoroethylene, 20 mol% of polymer units based on ethylene, and 28 mol % of polymer unitsbased on propylene. Further, the melting point was 96.2° C., the glasstransition temperature was 16.7° C., and the value Q at 140° C. was6.67.

PREPARATION EXAMPLE 2

Into a stainless steel autoclave having an internal capacity of 1.3 land equipped with a stirrer, 675 g of deionized water, 6.8 g of ananionic emulsifier (sodium lauryl sulfate, manufactured by NikkoChemical K.K.), 20.3 parts of a nonionic emulsifier (N-1120,manufactured by Nippon Nyukazai K.K.) and 33 g of t-butanol, werecharged, and deaeration by a vacuum pump and pressurizing with anitrogen gas were repeated to remove air. Then, 90 g oftetrafluoroethylene, 4.7 g of propylene and 3.2 g of ethylene wereintroduced into the autoclave.

When the internal temperature of the autoclave reached 65° C., thepressure was 2.68 MPa. Then, 5.8 cc of an aqueous solution containing20% of ammonium persulfate was added to initiate the reaction. Whilemaintaining the pressure by pressuring as the pressure decreased, 430 gof a gas mixture comprising 56 mol % of tetrafluoroethylene, 32 mol % ofpropylene and 12 mol % of ethylene, was continuously added to continuethe reaction.

Further, during the progress of the reaction, 12 cc of an aqueoussolution containing 20% of ammonium persulfate was continuously added. 8hours later, supply of the gas mixture was stopped, and the autoclavewas cooled with water to room temperature, whereupon an unreactedmonomer was purged, and the autoclave was opened to obtain an aqueousdispersion having a solid content concentration of 39.4%. The particlesize was 82 nm.

The obtained aqueous dispersion was precipitated by a centrifugalseparator, and the polymer was collected by a glass filter, and thecontained water was removed under a reduced pressure of 4 mmHg over aperiod of 5 hours, followed by pulverization by an impact hammer mill,to obtain a powder of a fluorocopolymer. From the results of theanalysis of the composition by ¹³C-NMR, this copolymer was found tocomprise 52 mol % of polymer units based on tetrafluoroethylene, 38 mol% of polymer units based on propylene and 10 mol % of polymer unitsbased on ethylene. The melting point was 49.2° C., and the glasstransition temperature was 6.7° C. Further, the value Q was 830.

PREPARATION EXAMPLE 3

Into a stainless steel autoclave having an internal capacity of 2.5 land equipped with a stirrer, 1,010 g of deionized water, 2.2 g ofpotassium carbonate (K₂CO₃), 32.2 g of a nonionic emulsifier (N-1110,manufactured by Nippon Nyukazai K.K.), 1.1 g of an anionic emulsifier(sodium lauryl sulfate), 46.6 g of t-butanol and 19.8 g of EOVE-1, werecharged, and deaeration by a vacuum pump and pressurizing with anitrogen gas were repeated to remove air. Then, 188 g oftetrafluoroethylene, 8 g of ethylene, 3.8 g of propylene and 5.1 g ofisobutylene were introduced into the autoclave.

When the internal temperature of the autoclave reached 70° C., thepressure was 15.4 kg/cm²G. Then, 2 cc of an aqueous solution containing25% of ammonium persulfate was added to initiate the reaction. Whilemaintaining the pressure by pressuring as the pressure decreased, 530 gof a gas mixture comprising 50 mol % of tetrafluoroethylene, 30 mol % ofethylene, 10 mol % of propylene and 10 mol % of isobutylene, wascontinuously added to continue the reaction.

Further, during the progress of the reaction, 30 cc of an aqueoussolution containing 25% of ammonium persulfate was continuously added.10 hours later, supply of the gas mixture was stopped, and the autoclavewas cooled with water to room temperature, whereupon an unreactedmonomer was purged, and the autoclave was opened to obtain an aqueousdispersion having a solid content concentration of 34.5 wt %. Theparticle size was 76 nm. The obtained aqueous dispersion wasprecipitated by a centrifugal separator, followed by filtration with aglass filter, and the contained water was removed under a reducedpressure of 4 mmHg over a period of 5 hours, followed by pulverizationby an impact hammer mill, to obtain a powder of a fluorocopolymer. Fromthe results of the analysis of the composition by ¹³ C-NMR, thiscopolymer was found to comprise 54 mol % of polymer units based ontetrafluoroethylene, 20 mol % of polymer units based on ethylene, 16 mol% of polymer units based on propylene and 9.5% of polymer units based onisobutylene. Further, the melting point was 102.3° C., the glasstransition temperature was 42.4° C., and the value Q at 140° C. was 1.3.

PREPARATION EXAMPLE 4

Into a stainless steel autoclave having an internal capacity of 1.3 land equipped with a stirrer, 810 g of deionized water, 8.1 g of afluorine type anionic emulsifier (FC-143, manufactured by Sumitomo 3MCompany), 2.4 g of a nonionic emulsifier (N-1120, manufactured by NipponNyukazai K.K.), 14.3 g of 4-hydroxybutyl vinyl ether (hereinafterreferred to as HBVE), 16.2 g of EOVE-1 and 40 g of t-butanol werecharged, and deaeration by a vacuum pump and pressurizing with anitrogen gas, were repeated to remove air. Then, 80 g oftetrafluoroethylene, 2.1 g of propylene and 3.3 g of ethylene wereintroduced into the autoclave.

When the internal temperature of the autoclave reached 65° C., thepressure was 2.34 MPa. Then, 6 cc of an aqueous solution containing 20%of ammonium persulfate was added to initiate the reaction. Whilemaintaining the pressure by pressurizing as the pressure decreased, 430g of a gas mixture comprising 53 mol % of tetrafluoroethylene, 27 mol %of propylene and 20 mol % of ethylene, was continuously added tocontinue the reaction.

Further, during the progress of the reaction, 12 cc of an aqueoussolution containing 20% of ammonium persulfate was continuously added.18 hours later, supply of the gas mixture was stopped, and the autoclavewas cooled with water to room temperature, whereupon an unreactedmonomer was purged, and the autoclave was opened to obtain an aqueousdispersion having a solid content concentration of 37.1%. The particlesize was 116 nm.

The obtained aqueous dispersion was precipitated by a centrifugalseparator, and the polymer was subjected to filtration with a glassfilter, and the contained water was removed under a reduce pressure of 4mmHg over a period of 5 hours, followed by pulverization by an impacthammer mill to obtain a powder of a fluorocopolymer. From the results ofthe analysis of the composition by ¹³C-NMR, this copolymer was found tocomprise 53 mol % of polymer units based on tetrafluoroethylene, 27 mol% of polymer units based on propylene, 17.5 mol % of polymer units basedon ethylene, 2 mol % of HBVE and 0.5 mol % of EOVE-1. The melting pointwas 89.8° C., and the glass transition temperature was 16.6° C. Further,the value Q at 140° C. was 25.

PREPARATION EXAMPLE 5

Into a stainless steel autoclave having an internal capacity of 1.3 land equipped with a stirrer, 90 parts of the aqueous dispersion of thefluorocopolymer obtained in Preparation Example 2, 616 parts ofdeionized water, 3.4 parts of potassium carbonate (K₂CO₃), 20.4 parts ofa nonionic emulsifier (N-1120, manufactured by Nippon Nyukazai K.K.),6.8 parts of an anionic emulsifier (sodium lauryl sulfate), and 33 g oft-butanol, were charged, and deaeration by a vacuum pump andpressurizing with a nitrogen gas, were repeated to remove air. Then, 83g of tetrafluoroethylene, 4.4 g of propylene and 2.9 g of ethylene wereintroduced into the autoclave.

When the internal temperature of the autoclave reached 65° C., thepressure was 2.62 MPa. Then, 2 cc of an aqueous solution containing 15%of ammonium persulfate was added to initiate the reaction. Whilemaintaining the pressure as the pressure decreased, 410 g of a gasmixture comprising 52 mol % of tetrafluoroethylene, 38 mol % ofpropylene and 10 mol % of ethylene, was continuously added to continuethe reaction.

Further, during the progress of the reaction, 30 cc of an aqueoussolution containing 15% of ammonium persulfate was continuously added.18 hours later, supply of the gas mixture was stopped, and the autoclavewas cooled with water to room temperature, whereupon an unreactedmonomer was purged, and the autoclave was opened to obtain an emulsionhaving a concentration of 34.5%. The particle size was 106 nm. Theobtained emulsion was precipitated by a centrifugal separator, and thepolymer was subjected to filtration with a glass filter, and thecontained water was removed under a reduced pressure of 4 mmHg over aperiod of 5 hours, followed by pulverization by an impact hammer mill,to obtain a powder of a fluorocopolymer. From the results of theanalysis of the composition by ¹³C-NNR, this copolymer was found tocomprise 52 mol % of polymer units based on tetrafluoroethylene, 38 mol% of polymer units based on propylene, and 10 mol % of polymerlunitsbased on ethylene. The melting point of this copolymer was 52.3° C. andthe glass transition temperature was 6.800. Further, the value Q was580.

PREPARATION EXAMPLE 6

An aqueous dispersion of a fluorocopolymer was obtained in accordancewith the method as disclosed in Preparation Examples 1 to 5 except thatthe monomer composition to be used for emulsion polymerization waschanged as identified in Table 1.

PREPARATION EXAMPLE 7

Into a glass flask having an internal capacity of 200 ml and equippedwith a thermometer, a stirrer and a reflux condenser, 70 g of an aqueousdispersion obtained by emulsion polymerization in the same mannlr as inExample 1 except that the monomer composition had proportions asidentified in Table 2, was charged (the amount of the fluorocopolymer inthe dispersion was 20 g), and heated to 80° C. When the temperaturereached 80° C., an aqueous dispersion prepared by emulsifying 10 g ofmethyl methacrylate, 1.2 g of isobutyl methacrylate, 0.04 g of anonionic emulsifier (N-1110, manufactured by Nippon Nyukazai K.K.), and0.02 g of an anionic emulsifier (sodium lauryl sulfate) with a 1 wt %aqueous solution, was dropwise added over a period of one hour.Immediately thereafter, 1 ml of an aqueous solution containing 2 wt % ofammonium persulfalte was added to initiate a reaction. Upon expirationof 3 hours of the reaction, the internal temperature off the flask wasraised to 90° C., and the reaction was continued for further one hour tocomplete the pollymerization, to obtain an aqueous dispersion having asolid content concentration of 40.8 wt % wherein the fluororesin and themethacrylate polymer were 2:1 (weight ratio). The results are shown inTable 2.

PREPARATION EXAMPLES 8 to 26

The fluorine-containing aquelous dispersions were obtained in accordancewith the method as disclosed in Preparation Examples 1 to 6 except thatthe monomer composition to be used for the/emulsion polymerization waschanged as shown in Table: 2 to 5.

TABLE 1 Monomers (mol %) Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 aTetrafluoroethylene  90/52 80/52 78.8/54   80/53 80/52 80/51 b Propylene3.5/28 10/38 3.8/16   5/27 10/38 5.0/21  c Ethylene 6.5/20 10/1012.0/20     12/17.5 10/10 8.5/16  d Isobutylene 3.8/9.5 9.5/18  6.5/11.5 e HBVE 12.3/2   f EOVE-1 1.6/0.5 3.1/0.5 g EOVE-2 0.5/0.5Melting point (° C.) 96.2 49.2 102.3 89.8 52.3 49.2 Glass transition16.7 6.7 42.4 16.6 6.8 6.7 temperature (° C.) Value Q 6.67 830 1.3 25580 250 Particle size (nm) 79 82 76 116 106 112

TABLE 2 Monomers (mol %) Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 aTetrafluoroethylene  90/52 80/52 80/54 83/53 80/53 80/51 b Propylene3.5/28 10/38 3.9/16   5/27 2.0/8.2 5.0/21  c Ethylene 6.5/20 10/1012.2/20   12/20 8.5/19  8.5/16  d Isobutylene 3.9/9.5 9.5/18   6.5/11.5e HBVE   2/1.8 f EOVE-1 0.5/0.5 g EOVE-2 0.5/0.5 Melting point (° C.)96.2 49.2 102.3 89.8 118.0 49.2 Glass transition 16.7 6.7 42.4 16.6 53.36.7 temperature (° C.) Value Q 25 1.2 650 480 105 0.9 Particle size (nm)78 69 92 103 112 101 Acrylic Methyl 90 90 90 90 90 monomers methacrylate(wt %) Isobutyl 10 10 10 10 10 methacrylate t-Butyl 100 methacrylateMelting point of the 73 52 80 64.3 97.8 — composite (° C.) Glasstransition 34 26 62.3 23.4 65.8 13.4 temperature of the composite (° C.)Value Q of the 150 68 2300 1200 890 3.5 composite Particle size of the98 87 112 123 135 120 composite (nm)

TABLE 3 Monomers (mol %) Ex. 13 Ex. 14 Ex. 15 a Tetrafluoroethylene 90/52 80/52   80/54 b Propylene 3.5/28 10/38  3.9/16 c Ethylene 6.5/2010/10 12.2/20 d Isobutylene  3.9/9.5 e HBVE f EOVE-1  0.5/0.5 g EOVE-2Melting point (° C.) 96.2 49.2 102.3 Glass transition 16.7 6.7 60.2temperature (° C.) Value Q 12 4.2 1028 Particle size (nm) 96 89 160 A-Methyl 90 cryl- methacrylate ic Isobutyl 95 90 5 mon- methacrylate o-Methacrylic acid 5 mers 2-Hydroxyethyl 10 (wt methacrylate %) γ- 5Trimethoxysilane methacrylate Melting point of the — 49.2 102.3composite (° C.) Glass transition 19.2 16.7 42.2 temperature of thecomposite (° C.) Value Q of the composite 239 494 1670 Particle size ofthe 118 125 186 composite (nm)

TABLE 4 Monomers (mol %) Ex. 16 Ex. 17 Ex. 18 Ex. 19 Ex. 20 Ex. 21 aTetrafluoroethylene  90/52 80/52 80/54 83/53 80/53 80/51 b Propylene3.5/28 10/38 3.9/16   5/27 2.0/8.2 5.0/21  c Ethylene 6.5/20 10/1012.2/20   12/20 8.5/19 8.5/16  d Isobutylene 3.9/9.5 9.5/18   6.5/11.5 eHBVE   2/1.8 f EOVE-1 0.5/0.5 g EOVE-2 0.5/0.5 Melting point (° C.) 96.249.2 102.3 89.8 118.0 49.2 Glass transition 16.7 6.7 42.4 16.6 53.3 6.7temperature (° C) Value Q 25 1.2 650 480 105 0.9 Particle size (nm) 7869 92 103 112 101 Acrylic Methyl 80 90 90 monomers methacrylate (wt %)Isobutyl 90 10 methacrylate t-Butyl 90 90 methacrylate Diacetone 10 1010 10 acrylamide Vinyl methyl 10 10 ketone Melting point of the 76 53 8360 90 49 composite (° C.) Glass transition 23 12 68 23 48 8.6temperature of the composite (° C.) Value Q of the 450 140 3400 1830 8503.4 composite Particle size of the 96 98 105 112 135 122 composite (nm)

TABLE 5 Monomers (mol %) Ex. 22 Ex. 23 Ex. 24 Ex. 25 Ex. 26 aTetrafluoroethylene  90/52 80/52 80/54 80/52 80/51 b Propylene 3.5/2810/38 3.9/16  10/38 c Ethylene 6.5/20 10/10 12.2/20   10/10 20/49 dIsobutylene 3.9/9.5 e HBVE f EOVE-1 0.5/0.5 g EOVE-2 Melting point (°C.) 96.2 49.2 102.3 49.2 270 Glass transition 16.7 6.7 42.4 6.7 —temperature (° C.) Value Q 25 1.2 650 1.2 — Particle size (nm) 78 69 9269 260 Acrylic Methyl 85 90 monomers methacrylate (wt %) Isobutyl 90 805 10 methacrylate Diacetone 5 5 acrylamide Vinyl methyl 10 ketoneMethacrylic acid 5 2-Hydroxyethyl 10 methacrylate γ-Trimethoxysilane 5methacrylate Melting point of the 88 56 97 52 — composite (° C.) Glasstransition 23 12 66 18 — temperature of the composite (° C.) Value Q ofthe composite 390 8.5 830 33 — Particle size of the 98 87 108 96 —composite (nm) The abbreviations in Tables 1 to 5 are as follows.EOVE-1: CH₂═CHO—C₄H₈—O—(CH₂CH₂O)_(n)H (average molecular weight: 520),EOVE-2: CH₂═CHOCH₂-cyclo-C₆H₁₀—CH₂—O—(CH₂CH₂O)_(n)H (average molecularweight: 830) HBVE: 4-hydroxybutyl vinyl ether

Further, the melting point and the glass transition temperature weredetermined by obtaining a heat generation peak when a sample was heatedat a rate of 10° C./min by a differential scanning calorimeter andtaking the temperatures at that time as the melting point and the glasstransition temperature. When the distribution of the peak of the meltingpoint was broad, the lowest point of the downwardly projected portionwas taken as the melting point.

Further, in the compositions for a, b, c, d, e and f, for example, thecomposition of tetrafluoroethylene being “90/52” indicates that “90” asthe numerator represents that the composition in the feed materialmonomer is 90 mol %, and “52” as the denominator represents that thepolymer units based on tetrafluoroethylene in the copolymer are 52 mol%.

EXAMPLES 1 to 15 and COMPARATIVE EXAMPLE 1

A clear coating material was formulated using 71 parts of an aqueousdispersion of the fluorocopolymer obtained as described above(Preparation Examples 1 to 15 and 26), 5.4 parts of a film-formingco-agent, 0.3 part of a thickener, 0.8 part of dispersant, 0.6 part of adefoaming agent and 10.3 parts of deionized water. The film-formingco-agent was Cs-12 (manufactured by Chisso Company); the thickener wasRheobis CR (manufactured by Hoechst Gosei K.K.), the dispersant wasNoscospas 44-C (manufactured by Sun-Nopco Company); and the defoamingagent was FS Antifoam 90 (manufactured by Dow Corning Company).

Such a coating material was coated on an aluminum plate by an air sprayso that the dried film thickness would be 40 μm and dried at 80° C. for30 minutes to obtain a test specimen. When the aqueous dispersion ofExample 26 was employed, no film was formed, whereby no test specimenwas obtained. With respect to such a test specimen, tests on weatherresistance, water resistance and stain resistance were carried out.

Evaluation of the weather resistance: After 3,000 hours of the QUV testemploying a fluorescent ultraviolet ray weather resistance testermanufactured by Q Panel Company, one having the gloss remarkablydeteriorated was identified with symbol X, and one having no substantialdeterioration of gloss observed, was identified with symbol ◯.

Evaluation of the water resistance: After immersion in warm water of 60°C. for one week, evaluation was made by the presence or absence ofpeeling or blistering of the coating film.

The results are shown in Table 6.

TABLE 6 Film- Preparation forming Weather Water No. Example propertiesresistance resistance Ex.  1 1 ∘ ∘ ∘  2 2 ∘ ∘ ∘  3 3 ∘ ∘ ∘  4 4 ∘ ∘ ∘  55 ∘ ∘ ∘  6 6 ∘ ∘ ∘  7 7 ∘ ∘ ∘  8 8 ∘ ∘ ∘  9 9 ∘ ∘ ∘ 10 10 ∘ ∘ ∘ 11 11 ∘∘ ∘ 12 12 ∘ ∘ ∘ 13 13 ∘ ∘ ∘ 14 14 ∘ ∘ ∘ 15 15 ∘ ∘ ∘ Comp.  1 26 x — —Ex.

EXAMPLES 16 to 18

A clear coating material was formulated using 71 parts of the aqueousdispersion of the fluorocopolymer of preparation example 1, 2 or 3, 3.5parts of lithium silicate (SiO₂/Li₂O molar ratio: 4.5; lithium silicate45, manufacatured by Nissan Chemical), 5.4 parts of a film-formingco-agent, 0.3 part of a thickener, 0.8 part of a dispersant, 0.6 part ofa defoaming agent, and 10.3 parts of deionized water, in the amounts asidentified in Table 7. Here, the film-forming co-agent was Cs-12 (ChissoCompany); the thickener was Rheobis CR (manufactured by Hoechst GoseiK.K.); the dispersant was Noscospas 44-C (manufactured by Sun-NopcoCompany); and the defoaming agent was FS Antifoam 90 (manufactured byDow Corning Company).

EXAMPLES 19 to 21

A clear coating material was formulated using 71 parts of the aqueousdispersion of the fluorocopolymer of Preparation Example 4 to 6, 3.5parts of colloidal silica (Snowtex C-20, manufactured by NissanChemical), 5.4 parts of a film-forming co-agent, 0.3 part of athickener, 0.8 part of a dispersant, 0.6 part of a defoaming agent and10.3 parts of deionized water, in the amounts as shown in Table 7. Here,the film-forming co-agent was Cs-12 (manufactured by Chisso Company);the thickener was Rheobis CR (manufactured by Hoechst Gosei K.K.); thedispersant was Noscospas 44-C (manufactured by Sun-Nopco Company); andthe defoaming agent was FS ntifoam 90 (manufactured by Dow CorningCompany).

EXAMPLES 22 to 24

A clear coating material was formulated using 71 arts of the aqueousdispersion of the fluorocopolymer of reparation Example 7 to 9, 7 partsof ethyl silicate (Ethyl Silicate 40, manufactured by Colcoat Company),5.4 parts of film-forming co-agent, 0.3 part of a thickener, 0.8 part ofa dispersant, 0.6 part of a defoaming agent and 10.3 parts of deionizedwater, in the amounts as identified in Table 7 or 8. Here, thefilm-forming co-agent was Cs-12 (manufactured by Chisso Company); thethickener was Rheobis CR (manufactured by Hoechst Gosei K.K.); thedispersant was Noscospas 44-C (manufactured by Sun-Nopco Company); andthe defoaming agent was FS Antifoam 90 (manufactured by Dow CorningCompany).

COMPARATIVE EXAMPLE 2

A clear coating material was formulated using 71 parts of the aqueousdispersion of the fluorocopolymer of Preparation Example 26, 7 parts ofethyl silicate (Ethyl Silicate 40, manufactured by Colcoat Company), 5.4parts of a film-forming co-agent, 0.3 part of a thickener, 0.8 part of adispersant, 0.6 part of a defoaming agent and 10.3 parts of deionizedwater, in the amounts as shown in Table 8. Here, the film-formingco-agent was Cs-12 (manufactured by Chisso Company); the thickener wasRheobis CR (manufactured by Hoechst Gosei K.K.); the dispersant wasNoscospas 44-C (manufactured by Sun-Nopco Company); and the defoamingagent was FS Antifoam 90 (manufactured by Dow Corning Company).

COMPARATIVE EXAMPLE 3

A clear coating material was formulated using 71 parts of the aqueousdispersion of the fluorocopolymer of Preparation Example 1, 5.4 parts ofa film-forming co-agent, 0.3 part of a thickener, 0.8 part of adispersant, 0.6 part of a defoaming agent and 10.3 parts of deionizedwater, in the amounts as shown in Table 8.

Here, the film-forming co-agent was Cs-12 (manufactured by ChissoCompany); the thickener was Rheobis CR (manufactured by Hoechst GoseiK.K.); the dispersant was Noscospas 44-C (manufactured by Sun-NopcoCompany); and the defoaming agent was FS Antifoam 90 (manufactured byDow Corning Company).

TABLE 7 Ex. 16 Ex. 17 Ex. 18 Ex. 19 Ex. 20 Ex. 21 Ex. 22 Pre. Pre. Pre.Pre. Pre. Pre. Pre. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7Fluorocopolymer dispersion 71 66 68 70 71 68 71 Lithium silicate 3.5 3.53.5 — — — — Colloidal silica — — 3.5 3.5 3.5 — Ethyl silicate — — — — —7 Film-forming co-agent 7 7 7 7 7 7 7 Thickener 5.4 5.4 5.4 5.4 5.4 5.45.4 Dispersant 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Defoaming agent 0.8 0.8 0.80.8 0.8 0.8 0.8 Deionized water 10.3 15.4 13.3 11.8 10.8 13.3 10.8

TABLE 8 Comp. Comp. Ex. 23 Ex. 24 Ex. 2 Ex. 3 Pre. Pre. Pre. Pre. Ex. 8Ex. 9 Ex. 26 Ex. 1 Fluorocopolymer 71 66 68 71 dispersion Lithium — — —— silicate Colloidal — — 3.5 — silica Ethyl silicate 7 7 — —Film-forming 7 7 7 7 co-agent Thickener 5.4 5.4 5.4 5.4 Dispersant 0.30.3 0.3 0.3 Defoaming agent 0.8 0.8 0.8 0.8 Deionized water 10.3 15.413.3 10.8

Such a coating material was coated on an aluminum plate by an air sprayso that the dried film thickness would be 40 μm and dried at 80° C. for30 minutes to obtain a test specimen. When the aqueous dispersion ofComparative Example 2 was used, no film was formed, and no test specimenwas obtained. With respect to such a test specimen, tests on weatherresistance, water resistance and stain resistance were carried out.

Stain resistance: Exposure was carried out outdoors at an angle of 45°facing south for one year, whereupon one wherein the color differenceafter wiping water from the stored plate was less than 2, was identifiedwith symbol ◯, one wherein the color difference was from 2 to 5 wasidentified with symbol Δ, and one wherein the color difference exceeded5, was identified with symbol X.

Adhesion: A tape peel test was carried out in accordance with JIS K5400.

The results are shown in Table 9.

TABLE 9 Aqueous Film- dispersion forming Weather Water Stain No. liquidproperties resistance resistance resistance Adhesion Ex. 16 Pre. Ex. 1 ∘∘ ∘ ∘ 100/100 17 Pre. Ex. 2 ∘ ∘ ∘ ∘ 100/100 18 Pre. Ex. 3 ∘ ∘ ∘ ∘100/100 19 Pre. Ex. 4 ∘ ∘ ∘ ∘ 100/100 20 Pre. Ex. 5 ∘ ∘ ∘ ∘ 100/100 21Pre. Ex. 6 ∘ ∘ ∘ ∘ 100/100 22 Pre. Ex. 7 ∘ ∘ ∘ ∘ 100/100 23 Pre. Ex. 8 ∘∘ ∘ ∘ 100/100 24 Pre. Ex. 9 ∘ ∘ ∘ ∘ 100/100 Comp.  2 Pre. Ex. 26 x — — —— Ex.  3 Pre. Ex. 1 ∘ ∘ ∘ Δ  80/100

EXAMPLE 25

A clear coating material was formulated using 71 parts of the aqueousdispersion of the fluorocopolymer of Preparation Example 16, 7 parts ofethyl silicate (Ethyl Silicate 40, manufactured by Colcoat Company), 5.4parts of a film-forming co-agent, 0.3 part of a thickener, 0.8 part of adispersant, 0.6 part of a defoaming agent, 0.6 part of adipic aciddehydrate, and 10.3 parts of deionized water, in the amounts as shown inTable 2. Here, the film-forming co-agent was Cs-12 (manufactured byChisso Company); the thickener was Rheobis CR (manufactured by HoechstGosei K.K.); the dispersant was Noscospas 44-C (manufactured bySun-Nopco Company); and the defoaming agent was FS Antifoam 90(manufactured by Dow Corning Company).

EXAMPLES 26 to 33 and COMPARATIVE EXAMPLES 4 to 5

Fluorine-containing water-based coating compositions were formulated inthe same manner as in Example 25 except that the blending proportionswere changed as shown in Table 10 or 11.

TABLE 10 Ex. 25 Ex. 26 Ex. 27 Ex. 28 Ex. 29 Ex. 30 Ex. 31 Pre. Pre. Pre.Pre. Pre. Pre. Pre. Ex. 16 Ex. 17 Ex. 18 Ex. 19 Ex. 20 Ex. 21 Ex. 22Fluorocopolymer dispersion 71 66 68 70 71 68 71 Film-forming co-agent 77 7 7 7 7 7 Thickener 5.4 5.4 5.4 5.4 5.4 5.4 5.4 Dispersant 0.3 0.3 0.30.3 0.3 0.3 0.3 Defoaming agent 0.8 0.8 0.8 0.8 0.8 0.8 0.8 Colloidalsilica 3.5 3.5 3.5 3.5 3.5 Ethyl Silicate 40 7 7 Adipic acid dihydrazide0.6 0.6 0.6 0.6 0.6 Isophthalic acid dihydrazide 0.6 0.6 Deionized water10.8 15.4 13.3 11.8 10.8 13.3 10.8

TABLE 11 Comp. Comp. Ex. 32 Ex. 33 Ex. 4 Ex. 5 Pre. Ex. Pre. Ex. Pre.Ex. Pre. Ex. 23 24 25 16 Fluorocopolymer 71 66 68 70 dispersionFilm-forming co-agent 7 7 7 7 Thickener 5.4 5.4 5.4 5.4 Dispersant 0.30.3 0.3 0.3 Defoaming agent 0.8 0.8 0.8 0.8 Colloidal silica 3.5 3.5Ethyl Silicate 40 7 7 Adipic acid dihydrazide 0.6 0.6 0.6 Isophthalicacid dihydrazide Deionized water 10.8 15.4 13.3 11.8

Such a coating material was coated on an aluminum plate by an air sprayso that the dried film thickness would be 40 μm, and dried at 80° C. for30 minutes to obtain a test specimen. With respect to such a testspecimen, tests on weather resistance, water resistance, solventresistance and stain resistance were carried out.

The results are shown in Table 12.

TABLE 12 Aqueous dispersion Weather Water Solvent Stain No. liquidresistance resistance resistance resistance Adhesion Ex. 1 Pre. Ex. 1 ∘∘ ∘ ∘ 100/100 2 Pre. Ex. 2 ∘ ∘ ∘ ∘ 100/100 3 Pre. Ex. 3 ∘ ∘ ∘ ∘ 100/1004 Pre. Ex. 4 ∘ ∘ ∘ ∘ 100/100 5 Pre. Ex. 5 ∘ ∘ ∘ ∘ 100/100 6 Pre. Ex. 6 ∘∘ ∘ ∘ 100/100 7 Pre. Ex. 7 ∘ ∘ ∘ ∘ 100/100 8 Pre. Ex. 8 ∘ ∘ ∘ ∘ 100/1009 Pre. Ex. 9 ∘ ∘ ∘ ∘ 100/100 Comp. 1 Pre. Ex. 10 ∘ x x ∘  80/100 Ex. 2Pre. Ex. 1 ∘ x x x  80/100

The aqueous dispersion of the fluorocopolymer of the present inventiongives a coating film excellent in weather resistance, stain resistance,water resistance, solvent resistance and adhesion and thus is veryuseful as a material for weather resistant water-based coating material.

Further, a water-based coating material employing the aqueous dispersionof the present invention is one using a stable aqueous dispersion as thebase basically without using an organic solvent, and accordingly, it isapplicable to a wide range of applications without restrictions such assolvent regulations. For example, it is particularly useful for weatherresistant coating of an exterior inorganic building material such asglass, metal or cement.

What is claimed is:
 1. An aqueous dispersion characterized in that afluorocopolymer which is a copolymer comprising (a) polymer units basedon a fluoroolefin, (b) polymer units based on propylene, and (c) polymerunits based on ethylene and/or (d) polymer units based on butylene andwhich has a melting point within a range of from 40 to 150° C., isdispersed in water.
 2. An aqueous dispersion characterized in that afluorocopolymer which is the fluorocopolymer as defined in claim 1 andwhich has a glass transition temperature within a range of from −20° C.to +80° C., is dispersed in water.
 3. An aqueous dispersioncharacterized in that a fluorocopolymer which is the fluorocopolymer asdefined in claim 1 and which has a value Q as an index of its molecularweight within a range of from 0.1 to 10,000, is dispersed in water,provided that the value Q is a value defined by a volume extruded in aunit time (mm³/sec), when, using a flow tester, the fluorocopolymer isfilled in a cylinder having an inner diameter of 11.3 mm and thenextruded from a nozzle having an inner diameter of 2.1 mm and a lengthof 8 mm under a load of 7 kg at 140° C.
 4. An aqueous dispersioncharacterized in that a fluorocopolymer which is the fluorocopolymer asdefined in claim 1 and which has a content of fluorine atoms within arange of from 20 to 65 wt %, is dispersed in water.
 5. An aqueousdispersion characterized in that a fluorocopolymer which is thefluorocopolymer as defined in claim 1 and which has a particle sizewithin a range of from 50 nm to 300 nm, is dispersed in water.
 6. Anaqueous dispersion obtained by emulsion polymerization, in the presenceof 100 parts by weight of particles of the fluorocopolymer as defined inclaim 1 of from 100 to 10,000 parts by weight of a mixture of the samecombination of monomers as for said particles.
 7. An aqueous dispersioncharacterized in that composite particles obtained by emulsionpolymerization of from 5 to 200 parts by weight of a radicalpolymerizable monomer mixture comprising, as the main component, analkyl (meth)acrylate having a C₁₋₁₈ alkyl group, in the presence of 100parts by weight of particles of the fluorocopolymer as defined in claim1 are dispersed in water.
 8. A composition for water-based coatingmaterial, comprising the aqueous dispersion of the fluorocopolymer asdefined in claim 1 and from 0.1 to 100 parts by weight, per 100 parts byweight of the solid content of the fluorocopolymer, of the solid contentof an inorganic and/or organic silicon compound, incorporated to theaqueous dispersion.
 9. A composition for water-based coating material,comprising the aqueous dispersion as defined in claim 7 and from 0.1 to100 parts by weight, per 100 parts by weight of the solid content of thecomposite particles, of the solid content of an inorganic and/or organicsilicon compound, incorporated to the aqueous dispersion.
 10. Acomposition for water-based coating material, comprising the aqueousdispersion as defined in claim 7 and a hydrazine derivative having atleast two hydrazine residues, incorporated to the aqueous dispersion.11. An aqueous dispersion characterized in that a fluorocopolymer whichis a copolymer comprising (a) polymer units based on a fluoroolefin, (b)polymer units based on propylene, (c) polymer units based on ethyleneand/or (d) polymer units based on butylene, and (e) polymer units basedon at least one member selected from a vinyl ester, a vinyl ether, anisopropenyl ether and an allyl ether and which has a melting pointwithin a range of from 40 to 150° C., is dispersed in water.
 12. Anaqueous dispersion characterized in that a fluorocopolymer which is thefluorocopolymer as defined in claim 11 and which has a glass transitiontemperature within a range of from −20° C. to +80° C., is dispersed inwater.
 13. An aqueous dispersion characterized in that a fluorocopolymerwhich is the fluorocopolymer as defined in claim 11 and which has avalue Q as an index of its molecular weight within a range of from 0.1to 10,000, is dispersed in water, provided that the value Q is a valuedefined by a volume extruded in a unit time (mm³/sec) when, using a flowtester, the fluorocopolymer is filled in a cylinder having an innerdiameter of 11.3 mm and then extruded from a nozzle having an innerdiameter of 2.1 mm and a length of 8 mm under a load of 7 kg at 140° C.14. An aqueous dispersion characterized in that a fluorocopolymer whichis the fluorocopolymer as defined in claim 11 and which has a particlesize within a range of from 50 nm to 300 nm, is dispersed in water. 15.An aqueous dispersion characterized in that a fluorocopolymer which isthe fluorocopolymer as defined in claim 11 and which has a content offluorine atoms within a range of from 20 to 65 wt %, is dispersed inwater.
 16. An aqueous dispersion obtained by emulsion polymerization, inthe presence of 100 parts by weight of particles of the fluorocopolymeras defined in claim 11, of from 100 to 10,000 parts by weight of amixture of the same combination of monomers as for said particles. 17.An aqueous dispersion characterized in that composite particles obtainedby emulsion polymerization of from 5 to 200 parts by weight of a radicalpolymerizable monomer mixture comprising, as the main component, analkyl (meth)acrylate having a C₁₋₁₈ alkyl group, in the presence of 100parts by weight of particles of the fluorocopolymer as defined in claim11, are dispersed in water.
 18. A composition for water-based coatingmaterial, comprising the aqueous dispersion of the fluorocopolymer asdefined in claim 11 and from 0.1 to 100 parts by weight, per 100 partsby weight of the solid content of the fluorocopolymer, of the solidcontent of an inorganic and/or organic silicon compound, incorporated tothe aqueous dispersion.
 19. A composition for water-based coatingmaterial, comprising the aqueous dispersion as defined in claim 17 andfrom 0.1 to 100 parts by weight, per 100 parts by weight of the solidcontent of the composite particles, of the solid content of an inorganicand/or organic silicon compound, incorporated to the aqueous dispersion.20. A composition for water-based coating material, comprising theaqueous dispersion as defined in claim 17 and a hydrazine derivativehaving at least two hydrazine residues, incorporated to the aqueousdispersion.
 21. An aqueous dispersion characterized in that afluorocopolymer which is a copolymer comprising (a) polymer units basedon a fluoroolefin, (b) polymer units based on propylene, (c) polymerunits based on ethylene and/or (d) polymer units based on butylene, and(f) polymer units based on a hydrophilic macro monomer represented bythe general formula: X-Y-Z (wherein X is a radical polymerizableunsaturated group, Y is a hydrophobic bivalent connecting group, and Zis a hydrophilic group) and which has a melting point within a range offrom 40 to 150° C., is dispersed in water.
 22. An aqueous dispersioncharacterized in that a fluorocopolymer which is the fluorocopolymer asdefined in claim 21 and which has a glass transition temperature withina range of from −20° C. to +80° C., is dispersed in water.
 23. Anaqueous dispersion characterized in that a fluorocopolymer which is thefluorocopolymer as defined in claim 21 and which has a value Q as anindex of its molecular weight within a range of from 0.1 to 10,000, isdispersed in water, provided that the value Q is a value defined by avolume extruded in a unit time (mm³/sec), when, using a flow tester, thefluorocopolymer is filled in a cylinder having an inner diameter of 11.3mm and then extruded from a nozzle having an inner diameter of 2.1 mmand a length of 8 mm under a load of 7 kg at 140° C.
 24. An aqueousdispersion characterized in that a fluorocopolymer which is thefluorocopolymer as defined in claim 21 and which has a particle sizewithin a range of from 50 nm to 300 nm, is dispersed in water.
 25. Anaqueous dispersion characterized in that a fluorocopolymer which is thefluorocopolymer as defined in claim 21 and which has a content offluorine atoms within a range of from 20 to 65 wt %, is dispersed inwater.
 26. An aqueous dispersion obtained by emulsion polymerization, inthe presence of 100 parts by weight of particles of the fluorocopolymeras defined in claim 21, of from 100 to 10,000 parts by weight of amixture of the same combination of monomers as for said particles. 27.An aqueous dispersion characterized in that composite particles obtainedby emulsion polymerization of from 5 to 200 parts by weight of a radicalpolymerizable monomer mixture comprising, as the main component, analkyl (meth)acrylate having a C₁₋₁₈ alkyl group, in the presence of 100parts by weight of particles of the fluorocopolymer as defined in claim21, are dispersed in water.
 28. A composition for water-based coatingmaterial, comprising the aqueous dispersion of the fluorocopolymer asdefined in claim 21 and from 0.1 to 100 parts by weight, per 100 partsby weight of the solid content of the fluorocopolymer, of the solidcontent of an inorganic and/or organic silicon compound, incorporated tothe aqueous dispersion.
 29. A composition for water-based coatingmaterial, comprising the aqueous dispersion as defined in claim 27 andfrom 0.1 to 100 parts by weight, per 100 parts by weight of the solidcontent of the composite particles, of the solid content of an inorganicand/or organic silicon compound, incorporated to the aqueous dispersion.30. A composition for water-based coating material, comprising theaqueous dispersion as defined in claim 27 and a hydrazine derivativehaving at least two hydrazine residues, incorporated to the aqueousdispersion.
 31. An aqueous dispersion characterized in that afluorocopolymer which is a copolymer comprising (a) polymer units basedon a fluoroolefin, (b) polymer units based on propylene, (c) polymerunits based on ethylene and/or (d) polymer units based on butylene, (e)polymer units of at least one member selected from a vinyl ester, avinyl ether, an isopropenyl ether and an allyl ether, and (f) polymerunits based on a hydrophilic macro monomer represented by the generalformula: X-Y-Z wherein X is a radical polymerizable unsaturated group, Yis a hydrophobic bivalent connecting group, and Z is a hydrophilic groupand which has a melting point within a range of from 40 to 150° C., isdispersed in water.
 32. An aqueous dispersion characterized in that afluorocopolymer which is the fluorocopolymer as defined in claim 31 andwhich has a glass transition temperature within a range of from −20° C.to +80° C., is dispersed in water.
 33. An aqueous dispersioncharacterized in that a fluorocopolymer which is the fluorocopolymer asdefined in claim 31 and which has a value Q as an index of its molecularweight within a range of from 0.1 to 10,000, is dispersed in water,provided that the value Q is a value defined by a volume extruded in aunit time (mm³/sec), when, using a flow tester, the fluorocopolymer isfilled in a cylinder having an inner diameter of 11.3 mm and thenextruded from a nozzle having an inner diameter of 2.1 mm and a lengthof 8 mm under a load of 7 kg at 140° C.
 34. An aqueous dispersioncharacterized in that a fluorocopolymer which is the fluorocopolymer asdefined in claim 31 and which has a particle size within a range of from50 nm to 300 nm, is dispersed in water.
 35. An aqueous dispersioncharacterized in that a fluorocopolymer which is the fluorocopolymer asdefined in claim 31 and which has a content of fluorine atoms within arange of from 20 to 65 wt %, is dispersed in water.
 36. An aqueousdispersion obtained by emulsion polymerization, in the presence of 100parts by weight of particles of the fluorocopolymer as defined in claim31, of from 100 to 10,000 parts by weight of a mixture of the samecombination of monomers as for said particles.
 37. An aqueous dispersioncharacterized in that composite particles obtained by emulsionpolymerization of from 5 to 200 parts by weight of a radicalpolymerizable monomer mixture comprising, as the main component, analkyl (meth)acrylate having a C₁₋₁₈ alkyl group, in the presence of 100parts by weight of particles of the fluorocopolymer as defined in claim31, are dispersed in water.
 38. A composition for water-based coatingmaterial, comprising the aqueous dispersion of the fluorocopolymer asdefined in claim 31 and from 0.1 to 100 parts by weight, per 100 partsby weight of the solid content of the fluorocopolymer, of the solidcontent of an inorganic and/or organic silicon compound, incorporated tothe aqueous dispersion.
 39. A composition for water-based coatingmaterial, comprising the aqueous dispersion as defined in claim 37 andfrom 0.1 to 100 parts by weight, per 100 parts by weight of the solidcontent of the composite particles, of the solid content of an inorganicand/or organic silicon compound, incorporated to the aqueous dispersion.40. A composition for water-based coating material, comprising theaqueous dispersion as defined in claim 37 and a hydrazine derivativehaving at least two hydrazine residues, incorporated to the aqueousdispersion.
 41. A composition for water-based coating material,comprising an aqueous dispersion of a fluorocopolymer obtained byemulsion polymerization of from 5 to 100 parts by weight of a radicalpolymerizable monomer mixture comprising (j) a monomer comprising, asthe main component, an alkyl (meth)acrylate having a C₁₋₁₈ alkyl groupand (k) a carbonyl group-containing monomer, in the presence of 100parts by weight of particles of the fluorocopolymer as defined in claim1, and a hydrazine derivative containing at least two hydrazineresidues, incorporated to the aqueous dispersion.
 42. A composition forwater-based coating material, comprising an aqueous dispersion of afluorocopolymer obtained by emulsion polymerization of from 5 to 100parts by weight of a radical polymerizable monomer mixture comprising(j) a monomer comprising, as the main component, an alkyl (meth)acrylatehaving a C₁₋₁₈ alkyl group and (k) a carbonyl group-containing monomer,in the presence of 100 parts by weight of particles of thefluorocopolymer as defined in claim 1, and a hydrazine derivativecontaining at least two hydrazine residues, incorporated to the aqueousdispersion.
 43. A composition for water-based coating material,comprising an aqueous dispersion of a fluorocopolymer obtained byemulsion polymerization of from 5 to 100 parts by weight of a radicalpolymerizable monomer mixture comprising (j) a monomer comprising, asthe main component, an alkyl (meth)acrylate having a C₁₋₁₈ alkyl groupand (k) a carbonyl group-containing monomer, in the presence of 100parts by weight of particles of the fluorocopolymer as defined in claim21, and a hydrazine derivative containing at least two hydrazineresidues, incorporated to the aqueous dispersion.
 44. A composition forwater-based coating material, comprising an aqueous dispersion of afluorocopolymer obtained by emulsion polymerization of from 5 to 100parts by weight of a radical polymerizable monomer mixture comprising(j) a monomer comprising, as the main component, an alkyl (meth)acrylatehaving a C₁₋₁₈ alkyl group and (k) a carbonyl group-containing monomer,in the presence of 100 parts by weight of particles of thefluorocopolymer as defined in claim 31, and a hydrazine derivativecontaining at least two hydrazine residues, incorporated to the aqueousdispersion.